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How to cook the most delicious and simple slow cooker fish pie. Using a selection of frozen fish to keep the costs down and also cooking the mashed potatoes in the slow cooker, this is the easiest slow cooked fish pie ever!

Made with frozen pollock, smoked haddock and pink salmon, you will love the simple cheap ingredients that make this the most creamy and addictive fish pie.

slow cooker fish pie recipe
Slow Cooker Fish Pie Recipe
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Mixed Fish Pie

I was at Morrison’s about six months ago now, buying supplies for the fish that I wanted for some new air fryer and instant pot recipes. I think I bought the whole fish counter the frozen section and my favourite was the tilapia that I bought for instant pot whole fish and air fryer whole fish.

The fishmonger said there was no pollock, so I wondered to the other end and found the frozen fish section and found cute packs of pollock that I wanted for some filet o fish. Of course, I bought more pollock than I needed as I wanted to try more out, and I ended up with surplus.

Plus, add to this that I saw some cute bags of fish pie mix and knew that my fillet o fish leftovers along with these fish pie mixes will soon become delicious fish pie filling for the slow cooker.

So, if you see those cute bags of mixed fish pie filling, then note they make the most amazing ever fish pie and you can buy them freeze them and save them for cooking with at a later date.  

Or if feeding just 1-2 people you can make this slow cooked fish pie and freeze the leftovers and then reheat when you are craving fish pie.

Are You New To The Slow Cooker?

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This is perfect for you if you want to get more recipes for your slow cooker. Loaded with a lot of British classics and something for everyone.

Click here or on the banner above and you will have access to it in an instant.

Can You Cook Frozen Fish In A Slow Cooker?

Yes, you can cook frozen fish in the slow cooker. Unlike frozen chicken which you can’t cook in the slow cooker, fish is much smaller, flakes away and gets to the correct internal temperature much faster.

The downside of frozen fish in the slow cooker, is that it carries a lot of water, so it makes it much harder to make with a sauce and you can end up with watery fish pie.

Can You Cook Fish Pie From Frozen?

Yes, you can cook fish pie from frozen. This is especially good for like us, when you have spare fish pie and you have frozen it for another day and now you want to reheat it.

You can then reheat your fish pie in the microwave and then enjoy an effortless dinner.

Can You Overcook Fish In Slow Cooker?

Yes, you can overcook fish in the slow cooker. The issue with fish is its small, its flaky and its fast cooking compared to many other foods that you would cook in the slow cooker.

What I recommend is that you keep an eye on the cook time and make sure your fish is at flaky and not rubbery overcooked level.

Do I Need To Cook Fish Before Making Fish Pie?

No, fish doesn’t need to be cooked before making fish pie, but it does need to be diced. I.e. no placing large fish fillets into the slow cooker, instead dice them up before loading up.

Why Is My Fish Pie Watery?

Fish pie is watery, especially if you have used frozen fish, because of the water contained in the fish to bulk it up and not draining the fish before you slow cook it.

Let me show you an example, this is the excess water we drained from our frozen fish before loading it into the slow cooker:

watery fish pie

Just imagine if you have loaded the fish straight into the slow cooker and how watery your slow cooker fish pie would have become.

To prevent this, I load the fish once thawed into a sieve with a bowl below to catch the excess and leave it there for 20 minutes and then let the excess drip below:

How To Slow Cook Fish Pie?

Then you have fish carrying less water ready for slow cooking and then combined with making sure the fish pie is thick and creamy, your fish pie will not be watery.

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What Does Fish Pie Contain?

What Does Fish Pie Contain

Fish – We all have our own opinion of what fish should go in a fish pie. My grandad who was a fisherman believed it was whatever scraps they had leftover very much like his air fryer fishcakes. We are keeping it simple with 2 packs of Morrisons fish mix and 1 pack of Morrisons pollock.

Potatoes – A fish pie, just like a shepherd’s pie or a cottage pie, is not the same without the big portion of mashed potatoes on top. We are using a big bag of spuds and then cooking the mash first.

Philadelphia – The best way to thicken and make a creamy fish pie filling is with some Philadelphia. If you want a low fat fish pie i.e. you are on Slimming World then you can use lightest Philadelphia.

Stock – I also recommend some fish stock. It really gives the fish pie a delicious flavour or if you can’t get fish stock then you can swap it for our instant pot veggie stock. We used fish stock that was leftovers from our instant pot garlic mussels. I highly recommend when you make a fish dish that you save those leftovers and freeze them.

Peas – a fish pie just wouldn’t be the same without stirring in some frozen peas. We love the colour of the peas in this simple fish pie recipe.

Seasoning – Then for seasoning your mixed fish pie recipe we used salt, pepper, bouquet garni, and parsley.

Extras – Also to give your mixed fish pie recipe the wow factor, I also recommend some wensleydale, milk, and butter for the mashed potato topping.

Then for the kitchen gadgets that we have used in this slow cooked fish pie recipe it has just been our Crockpot. We have this one and its wonderful for many types of slow cooker recipes and also great for easy Sunday lunches.

Plus, we recommend you head over to our slow cooker recipes category as we have more than 100 tried and tested slow cooker recipes and have been using slow cookers for 18 years.

How To Slow Cook Fish Pie?

slow cooker fish pie step by step
  • Peel. Start by peeling and dicing your potatoes. Load them into the slow cooker with fish stock, butter, or margarine along with mixed herbs and salt and pepper. Let them slow cook for 90 minutes.
  • Prep. Just before the mash is ready, drain and thaw your fish and then dice into medium chunks.
  • Dump. Remove the potatoes from the slow cooker and load into a mixing bowl. In the meantime (no need to clean first) add your fish, fish stock, Philadelphia, and seasonings. Slow cook for 90 minutes or until the fish is flaky.
  • Mash. When the slow cooker is back on add margarine and any extra seasonings and some milk to the bowl and mash until you have creamy mash.
  • Creamy. When the slow cooker is done, stir the slow cooker and add in frozen peas and if not thick enough add in a little mashed potatoes as they are a natural creamy thickener. Do a taste test and if needed add in extra seasonings. You now have your fish pie filling.
  • Finish. Cover with mashed potatoes, and sprinkle with Wensleydale, then slow cook for the last hour before serving.  

And I am sure you can see why this recipe for fish pie is a true favourite of mine.

How Long To Cook Fish Pie?

Our fish pie cooking time is JUST 4 hours on high or 7 hours if using the low setting. We do this in three cooking stages including the making of the mashed potatoes, the fish pie filling, assembling your fish pie and cooking together.

White Sauce For Fish Pie

The beauty of the white sauce for the fish pie, is that it cooks and becomes lovely and creamy as the fish cooks. Meaning that you don’t need to make a separate fish sauce for your fish pie.

Then your hero ingredient is the Philadelphia cream cheese as this creates the creamy sauce.

White Sauce For Fish Pie

Freezing Fish Pie

For freezing fish pie, I highly recommend using some pyrex containers. They freeze really well and then you can use that same container (minus the lid) to reheat fish pie in the microwave.

More Delicious Fish Recipes

slow cooker fish pie

Your slow cooker fish pie recipe with frozen fish is below, note you can print it out with or without photos, adjust servings, or click between metric and imperial depending on where you are in the world.

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5 from 1 vote

Slow Cooker Fish Pie

How to cook the most delicious and simple slow cooker fish pie. Using a selection of frozen fish to keep the costs down and also cooking the mashed potatoes in the slow cooker, this is the easiest slow cooked fish pie ever!
Prep Time: 10 minutes
Cook Time: 4 hours
Total Time: 4 hours 10 minutes
Servings: 4
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Slow Cooker Mash

Fish Pie Filling

  • 800 g Fish Pie Mix
  • 6 Pollock Fillets
  • 480 ml Fish Stock
  • 2 Small Tubs Philadelphia Lightest
  • 2 Tbsp Parsley
  • 1 Tbsp Bouquet Garni
  • Salt & Pepper
  • 2 Cups Frozen Peas

Kitchen Gadgets:


  • Peel your potatoes and dice them and load the potatoes into the slow cooker with half the butter or margarine, salt, pepper, and mixed herbs and the fish stock. Allow to slow cook for 90 minutes on high to create soft mashed potatoes. After 90 minutes put the potatoes to one side in a suitable bowl and add the milk and other half of the butter.
    How To Slow Cook Fish Pie?
  • Whilst the potatoes are cooking in the slow cooker, place the fish fillets into a sieve, with a bowl below to catch the excess liquid. Sit the fish in the sieve for at least 20 minutes to drain any excess water and stop your fish pie from being watery. Then dice your fish into medium chunks.
    How To Slow Cook Fish Pie?
  • Load into the slow cooker your diced fish, soft cheese, fish stock, and seasonings. Slow cook your fish pie filling for 90 minutes on high.
    How To Slow Cook Fish Pie?
  • Whilst the slow cooker is working its magic, mash your potatoes with the butter, and milk until you have delicious creamy mash.
    How To Slow Cook Fish Pie?
  • When the slow cooker is done, stir and add in some extra mash if needed to make it creamier. Then add in the garden peas and mix well. The fish filling will now be nice and creamy.
    How To Slow Cook Fish Pie?
  • Load the mashed potatoes over the fish pie filling and then sprinkle with wensleydale. Slow cook for a last hour on high before serving.
    How To Slow Cook Fish Pie?


Fish. I highly recommend making a fish pie with frozen fish. Frozen fish if drained correctly makes a fantastic cheap and easy way to make fish pie. We used 2 400g bags of mixed fish from Morrisons which included pollock, smoked haddock and pink salmon. We then also used a bag of frozen pollock fillets.
Sauce. I always use a little mash potato as a natural thickener. It tastes so good, and you are already making mash to go with the pie so why not?
Stock. I love to use the leftovers from meals and make into frozen stock cubes. I always have a big batch in the freezer and in this recipe I used leftovers from an instant pot garlic mussels recipe.
Thanks for reading our fish pie recipe with frozen fish on Recipe This. We have many more slow cooker recipes for you to check out next. Though if you would like more slow cooker dinner recipes, do check out our slow cooker sausages and onion gravy recipe next.


Calories: 1891kcal | Carbohydrates: 58g | Protein: 271g | Fat: 58g | Saturated Fat: 17g | Polyunsaturated Fat: 15g | Monounsaturated Fat: 18g | Trans Fat: 0.2g | Cholesterol: 934mg | Sodium: 1258mg | Potassium: 6832mg | Fiber: 11g | Sugar: 7g | Vitamin A: 2275IU | Vitamin C: 94mg | Calcium: 542mg | Iron: 12mg
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slow cooker fish pie

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About Sam & Dom

Hi! I am Sam and along with my chef hubby Dom we love sharing with you easy everyday recipes using kitchen gadgets. We are also the authors of The Complete Air Fryer Cookbook, an amazing air fryer cookbook filled with 140+ everyday air fryer recipes.

Beyond the air fryer we also love the instant pot, slow cooker, soup maker, ninja foodi, pie marker and several other kitchen gadgets.

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Recipe Rating


  1. Can I ask what is “fish pie mix”?
    I am not from UK and we don’t have it here, so can I make this mix myself at home (gluten-free) do you think?

    1. Hi Kt Mae,

      Fish pie mix is just a mix of fish, cod, haddock, salmon, squid and sometimes it contains shell fish like prawns, mussels that kind of mix 🙂

  2. 5 stars
    We love a fish pie here in this household and never tried it in our slow cooker so i thought i would try your recipe instead of my tried and tested one because i did not think it would have worked in a slow cooker, but yours was really tasty and so easy to follow, it tasted amazing and everyone ate it all up, thank you.