Costco Mahi Mahi (How to Grill and Make a Fish Sandwich!)

Costco sells three pound bags of frozen Mahi Mahi filets and they are great to put on the grill!  The large, meaty filets pair up well with many types of seasoning and are firm enough that they don’t fall apart while grilling.

This review will cover everything you need to know about this fish including how to grill, calories and price at Costco.

Costco Mahi Mahi

What Comes in the Bag of Kirkland Signature Mahi Mahi

You get three pounds of boneless, skinless mahi mahi filets that are individually wrapped and frozen.

The fish is Wild Caught and a product of Ecuador.  For folks that do not like Farm Raised fish these filets will be perfect.

The package says to remove the filets from the vacuum packaging and let them thaw in the refrigerator overnight before cooking.  Our refrigerator must be too cold because it takes at least two days for the filets to thaw in ours.

I prefer to thaw the fish under cold running water.

The filets vary in size but typically weigh about 7-8 ounces which is a hearty portion.

Individual Mahi Mahi Filet

Season the Mahi Mahi Before Grilling

After the mahi mahi has thawed pat the filets dry with paper towels.

Apply a very thin layer of olive oil to help the seasoning adhere and then coat with your favorite seasoning.  Some nice suggestions are Blackened Redfish Seasoning by Paul Prudhomme or Traeger Fin and Feather Rub.

If you want to make your own seasoning blend then here is a recipe to try:

  • 1 tbls smoked paprika
  • 1 tsp salt
  • 1 tsp dried Italian herbs
  • 1 tsp lemon zest
  • 1 tsp brown sugar
  • 1 tsp black pepper

Seasoned Costco Mahi Mahi

Grill the Mahi Mahi on High Heat With a Weber Gas Grill

These filets cook up so fast that it doesn’t really make sense to fire up your Traeger or light a charcoal grill.  Instead, fire up your gas grill and let the grates preheat for 15 minutes.

If you are cooking on an “el cheapo grill” then I strongly suggest you look into a higher quality, longer lasting grill like the Genesis II E335 at Costco.

We had a set of GrillGrate panels on our grill to make flipping the fish easier but you don’t really need them.

Once the grill is hot put the fish on the grate and cook for five minutes.  Flip the fish over and grill for five more minutes.  The fish should be done at this point but go ahead and check with a digital thermometer to make sure it has reached an internal temperature of 145F.

Mahi Mahi on the Grill

Make the Grilled Mahi Mahi Sandwich!

I like using soft rolls for fish sandwiches and either a potato roll or a King’s Hawaiian roll are excellent choices.

Place a layer of mayonnaise (or tarter sauce) on the bottom roll then top with lettuce, slices of tomato and the grilled mahi mahi.  We like a little habanero/carrot based hot sauce on the top bun to put a spicy kick into the flavor party!

You can serve the sandwich with Cole slaw and chips to have a great little meal 🙂

The fish tastes clean, fresh and mild.  Mahi Mahi is not an oily fish so there is no strong fishy taste.

Grilled Mahi Mahi Sandwich

Grilled Mahi Mahi Sandwich

Grilled Costco Mahi Mahi Sandwich

Frozen Mahi Mahi filets from Costco are thawed, seasoned and grilled to create a pretty amazing sandwich!
Prep Time 30 minutes
Cook Time 10 minutes
Total Time 40 minutes
Course Main Course
Cuisine American
Calories 315 kcal


  • Weber Gas Grill


  • 8 ounce Mahi Mahi Filets per sandwich
  • 1 tbsp Seafood Seasoning of Choice per filet
  • 1 Soft Roll (potato or King's Hawaiian) per sandwich
  • 1 tbsp Mayonnaise (or Tarter Sauce)
  • Lettuce
  • Sliced Tomatoes


  • Thaw the number of desired mahi mahi filets either overnight in the refrigerator of under cold running water.
  • Pat the fish dry and apply a thin layer of olive oil to help the seasoning stick to the fish.
  • Apply the seasoning to both sides of the fish.
  • Heat you gas grill to High and let the grates get hot for 15 minutes,
  • Grill the seasoned mahi mahi for five minutes per side to an internal temperature of 145F.
  • Assemble the fish sandwich and serve with desired side dishes.
Keyword Costco Mahi Mahi

For another great fish recipe check out Traeger Smoked Catfish Filets!

Mahi Mahi Nutrition and Calories

A single serving of mahi mahi is 1/2 of a typical filet and has the following nutritional information:

  • Calories = 100
  • Fat = 1g
  • Cholesterol = 80mg
  • Sodium = 100mg
  • Carbohydrates = 0mg
  • Protein = 21g

Mahi mahi is ultra lean, low in cholesterol and packed in protein.  This makes it one of my favorite fish options at Costco.

Price of Frozen Mahi Mahi at Costco

The Kirkland Signature frozen Mahi Mahi is Item Number 251704 and is found in the freezer section of the warehouse.

The fish costs about $10 per pound so the three pound bag will cost about $30.

The price of $10 per pound is a heck of a lot cheaper than halibut and on par with the frozen cod and salmon.

Price of Frozen Mahi Mahi at Costco

More Fish Options at Costco

For more reviews of your frozen fish options at Costco please see the following:

Kirkland Everything Seasoned Cod Review

Trident Beer Battered Cod Review

Furikake Crusted Cod Review