Crab and Shrimp Casserole is a creamy, cheesy seafood bake with sweet crab, tender shrimp and a golden breadcrumb top. It is special enough for a holiday or company dinner, and simple enough for a Friday night at home.
How to make crab and shrimp casserole: Toss shrimp, crab, celery, onion and garlic with a quick cheddar-mayonnaise white sauce, spread it in a 9×13-inch dish, top with breadcrumbs and bake at 350°F for about 30 minutes.

Why You’ll Love It
- A generous seafood bake: a full pound each of shrimp and crab in one dish.
- Creamy and crisp: a cheddar sauce holds everything together under a crunchy crumb top.
- Short hands-on time: one bowl for the seafood, one saucepan for the sauce.
- Serves 6: enough for a dinner party with a salad on the side.
Ingredient Notes
Shrimp: Use 1 pound of raw shrimp, peeled and deveined. Thaw frozen shrimp completely and pat them dry, because extra water thins the sauce in the oven.
Crabmeat: Fresh or canned cooked crabmeat both work. Drain canned crab well and pick through it for shell. I fold it in gently so the lumps stay in pieces you can see.
Celery, onion and garlic: They go in raw and soften in the oven, and the celery keeps a little crunch. Dice them small so they cook evenly.
Mayonnaise and sharp cheddar: These go into the white sauce off the heat. The mayonnaise makes it rich and creamy, and sharp cheddar gives more flavor than mild in a dish this creamy.
Breadcrumbs: Half a cup is enough to cover the top in a thin, even layer that browns in 30 minutes.
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Ingredients
- 1 lb shrimp, raw, peeled and deveined (thawed if frozen)
- 1 lb cooked crabmeat, fresh or canned, well drained
- 1 cup celery, diced
- 1/2 cup onion, diced
- 2 cloves garlic, minced
- 2 tablespoons butter
- 2 tablespoons all-purpose flour
- 1 cup milk
- 1/2 cup mayonnaise
- 1 cup sharp cheddar cheese, grated
- 1/2 cup breadcrumbs
- 1 pinch salt and pepper, to taste
- 1 tablespoon fresh parsley, chopped, for garnish
How to Make Crab and Shrimp Casserole
1. Heat the oven. Preheat the oven to 350°F (175°C).
2. Mix the seafood. In a large bowl, combine the shrimp, crabmeat, celery, onion and garlic. Stir to mix evenly.
3. Make the sauce. In a medium saucepan over medium heat, melt the butter. Stir in the flour and cook for 1-2 minutes until golden and bubbly. Gradually whisk in the milk and keep stirring for 3-5 minutes until thickened. Remove from the heat and stir in the mayonnaise, cheddar cheese, salt and pepper.
4. Combine. Add the seafood mixture to the sauce and stir until evenly coated. Spread it in a greased 9×13-inch baking dish.
5. Top. Sprinkle the breadcrumbs evenly over the casserole.
6. Bake. Bake for about 30 minutes, until the top is bubbly and golden brown, the shrimp are firm and opaque, and the center reaches 165°F (74°C).
7. Serve. Let the casserole cool for a few minutes, then garnish with fresh parsley.
How to Tell the Shrimp Are Done
The shrimp go into the dish raw, so they cook in the oven along with everything else. Look at the shrimp you can see around the edges: they turn from gray and see-through to pink and opaque, and they feel firm when you press one with a spoon.
A golden top can fool you, because the crumbs brown before the center is hot. Check the middle of the dish with a thermometer for 165°F before you take it out.
I try not to go past that point. Shrimp that cook too long turn tight and rubbery, so as soon as the center is hot and the shrimp are opaque, the casserole is ready.
Tips for Success
Why is my seafood casserole watery?
Wet seafood is the usual cause. Drain the crab well and pat thawed shrimp dry before mixing, so the sauce stays thick and creamy.
Why is the sauce lumpy?
The milk went in too fast. Whisk it in gradually over medium heat and keep stirring until the sauce is smooth and thick.
Why did the top burn before the middle was hot?
The oven runs hot or the dish sat too high. Bake on the middle rack, and if the crumbs brown early, lay a loose sheet of foil over the top.
Variations
- Change the cheese: Monterey Jack or Gruyère melts well in the sauce in place of cheddar.
- Crisper top: use panko instead of regular breadcrumbs.
Storage & Reheating
USDA FSIS says to refrigerate leftovers within 2 hours in shallow, covered containers and use them within 3 to 4 days. Reheat portions until a food thermometer reads 165°F. The mayonnaise sauce can separate after freezing, so this casserole is best kept in the fridge.
What to Serve With It
A green salad or steamed vegetables and some garlic bread make it a full meal. For more seafood dinners, try the crab and shrimp seafood bisque, lobster, crab and shrimp mac and cheese or Red Lobster-style shrimp scampi. On busy nights, garlic Parmesan roasted shrimp, Cajun shrimp in foil and baked shrimp in lemon butter sauce are all quick.
Frequently Asked Questions
What gives shrimp casserole the best flavor?
A rich sauce and good seafood. Here sharp cheddar and mayonnaise season the creamy white sauce, garlic and onion add depth, and sweet crab balances the shrimp.
Can I use cooked shrimp?
Yes. Cooked shrimp only need to heat through, so they will not firm up further in the oven. Bake until the center reaches 165°F and take it out, so they do not overcook.
Can I assemble it ahead?
Make the sauce and mix the seafood up to a few hours ahead and keep them separate in the refrigerator. Combine them and add the crumbs right before baking.
Final Notes
Dry seafood is the secret to a thick, creamy casserole, so drain and pat before you mix. If you have a question or make it for dinner, tell me how it turned out in the comments.

Crab and Shrimp Casserole
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Ingredients
- 1 lb shrimp raw, peeled and deveined; thawed if frozen
- 1 lb cooked crabmeat fresh or canned, well drained
- 1 cup celery diced
- 1/2 cup onion diced
- 2 cloves garlic minced
- 2 tablespoons butter for the sauce
- 2 tablespoons all-purpose flour for the roux
- 1 cup milk
- 1/2 cup mayonnaise
- 1 cup sharp cheddar cheese grated
- 1/2 cup breadcrumbs for topping
- 1 pinch salt and pepper to taste
- 1 tablespoon fresh parsley chopped, for garnish
Instructions
- Set your oven to 350°F (175°C) to ensure it’s ready for baking.
- In a large mixing bowl, combine the shrimp, crabmeat, celery, onion, and minced garlic. Stir to mix evenly.
- In a medium saucepan over medium heat, melt the butter. Stir in the flour and cook for 1-2 minutes until golden and bubbly. Gradually whisk in the milk, stirring continuously for 3-5 minutes until thickened. Remove from heat and stir in mayonnaise, cheddar cheese, salt, and pepper.
- Add the seafood mixture to the creamy sauce, stirring until evenly coated. Spread in a greased 9x13-inch baking dish.
- Sprinkle breadcrumbs evenly over the casserole.
- Bake for about 30 minutes, until the top is bubbly and golden brown, the shrimp are firm and opaque, and the center reaches 165°F (74°C).
- Let the casserole cool for a few minutes, then garnish with fresh parsley. Serve warm with a side salad or steamed vegetables.
Notes
Nutrition
Nutrition values are estimates based on the listed ingredients and serving count. Actual values vary with brands, cuts and portion sizes.










