Best Ever Blackened Mahi-Mahi Fillets

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You will swoon over this easy recipe for the Best Ever Blackened Mahi-Mahi Fillets. Blanketed in a homemade cajun blackening seasoning mix and pan-seared in a screaming hot cast-iron skillet, these blackened mahi-mahi fillets are moist, with a crispy flavor-packed crust!

Like my Blackened Grouper, this recipe is super simple to prepare and super delicious. And the best part, you can have this fantastic seafood entree on the table in ten minutes. It’s a restaurant-style main dish that’s as perfect for a quick weeknight dinner as a dinner party.

Blackened mahi-mahi fillets on a white plate with cheese grits and broccoli slaw.

With firm, white, lean flesh that is slightly sweet and very mild, mahi-mahi is a versatile fish that is tasty whether it’s prepared blackened, fried, baked, pan-seared, broiled, or grilled.

Ingredients – here’s what you will need: (exact amounts are listed in the recipe card below)

Two mahi-mahi fillets along with a stick of butter and lemons.

Fresh mahi-mahi – skinned and cut into fillets. You can also substitute frozen mahi-mahi, but let it thaw and pat dry with a paper towel before cooking it.
Butter – coats the fish to help the seasoning stick and adds a rich flavor to the overall dish.
Fresh lemon juice – there is a scientific explanation, but the best reason is that it enhances the flavor of fish.

For the blackening seasoning you will need:

Spices including oregano and thyme as well as garlic and onion powder and paprika on a board to make blackened seasoning.

Cayenne and black pepper – provide a bit of heat.
Oregano, thyme, and cumin – provide a herby, earthy, smoky taste.
Garlic and onion powder – lend their unique flavors to the mix.
Paprika – adds a bit of color and smokiness.
Brown sugar – adds just a touch of sweetness that compliments the savory spices.
Kosher salt: enhances all of the flavors and brings everything together.

Directions – here’s how to make it:

Combine all blackening seasoning ingredients in a bowl and mix well. Store any leftover seasoning mix in an airtight container for future use.
Use a paper towel and pat dry the fillets.

Using a paper towel to pat dry two fish fillets.

Melt two tablespoons of butter. Use a pastry brush and coat both sides of the fillets.

Brushing butter on two fish fillets on a cutting board.

To season the mahi-mahi, top each fillet with a tablespoon of the blackening spice mix and rub it in with your fingers. Then, flip the fillet over and do the same thing on the other side.

Adding blackened seasoning to two fish fillets on a cutting board.

Add three tablespoons of butter (you can substitute olive oil) to a cast-iron skillet over medium-high heat.
Set your exhaust fan to high. Blackening fish will produce smoke. When the butter melts and the skillet is hot, add the fish and let cook undisturbed for 3 minutes.

Cooking fish fillets in a cast iron skillet.

Use a fish spatula or pancake-turner and turn the fillets over. Cook for another three to four minutes. You can tell when fish is cooked when the flesh turns opaque and flakes easily when pierced with a fork. Be careful not to overcook.

Two blackened fish fillets in a cast iron skillet.

Serve the blackened mahi-mahi hot with a squeeze of lemon juice over the top.

Blackened mahi-mahi served with cheese grits and broccoli salad with lemon garnish.

Frequently asked questions:

What is mahi-mahi?

Closely related to pompano and second only in beauty to red snapper with its gorgeous red coloring, mahi-mahi is one of the most stunning fish in the world, with iridescent blue, green, and gold coloring. If you wonder what’s the best way to cook mahi-mahi, it’s delicious whether it’s blackened, broiled, baked, or fried because of its mild, sweet flavor.

Mahi-mahi, which is found in warm waters worldwide including the Gulf of Mexico, is also called dolphin, dolphinfish, or dorado. But don’t worry, it is not related to Flipper or the mammal bottlenose dolphins.

According to the Florida Department of Agriculture, when shopping for mahi-mahi, “look for firm, slightly pink meat with a fresh sea-breeze aroma and no discoloration.”

Should you remove the skin and bloodline?

Mahi-mahi has a thick skin that will prevent the blackening seasoning from reaching the flesh. It should be removed for this recipe or you can ask your fishmonger to remove it for you.

Mahi-mahi, like bluefish and Spanish mackerel, naturally have a bloodline (darker red flesh) running down the length of the fillets. Most of the time, when you purchase fillets, this has already been removed. If not, you will want to cut that out. While a bloodline is safe to eat, it has a stronger taste and can make your fillets taste a little fishy.

What makes a fish blackened?

Blackening fish is simply coating it with a blend of blackening spices and searing it quickly over high heat in a cast-iron skillet until the spices are caramelized and form a deliciously tasty crust on the outside.

While most folks blacken their fish in a cast-iron skillet over a burner on the stove, you can also blacken it outside on a grill, blacken it in the oven, and even blacken it under a broiler.

What is blackening seasoning?

Blackening seasoning gives the mahi-mahi fillets their flavorful spicy taste, blackened crusty appearance, and a delicious crunch. My easy homemade cajun blackening seasoning recipe is full of spices including oregano, and cumin. I also include a touch of brown sugar and a little cayenne pepper for heat.

This delicious blackening seasoning mix can also be used on shrimp, chicken, beef, and pork. I’ve even been known to add a little to soups, stews, and various sauces. You can also substitute it for cajun or creole seasoning in recipes. I always keep a jar in my pantry.

You can also purchase premade blackening seasoning and will find it in your grocery store’s spice aisle. I like and have used both Old Bay and Chef Paul Prudhomme brands. Prudhomme was a chef from New Orleans credited with popularizing blackened seasoning as well as creole and cajun seasonings.

What to serve with it?

While some folks like to serve this dish with rice, my favorite side dishes to pair with blackened mahi-mahi are cheese grits, coleslaw, and hoecakes. It would also be delicious served with dirty rice, southern spicy tomato cheese grits or southern corn casserole, twice-baked sweet potatoes, green beans with new potatoes, southern potato salad, deviled eggs, or french fries.

Panzanella, Southern Cucumber and Tomato Salad, or my Summer Pasta Salad would also be excellent sides.

Variations:

While blackened mahi-mahi is delicious on its own, if you are like me and like to switch things up from time to time, you might consider topping it with a cajun cream sauce, or lemon butter sauce. It is also delicious topped with all kinds of salsas, including mango salsa, peach salsa, and pineapple salsa.

Sharon’s tips:

To make this recipe on a grill, preheat your grill to high, add your cast iron skillet, preheat it, and follow the directions for cooking it on the stove. The advantage of cooking it outside is that you won’t have a smoky kitchen if you don’t have a good exhaust fan.
The recipe for blackened seasoning, as written, is a little spicy. If you want to lower the heat, reduce the amount of cayenne pepper, or eliminate it.
For the most authentic flavor and crunch, use a cast-iron skillet. Of course, a regular non-stick skillet works too, but you might not get the crispy exterior.
Besides mahi-mahi, Redfish is probably the most well-known blackened fish. However, you can also substitute any firm white fish such as halibut, grouper, snapper, corvina (a type of drum), or seabass for the mahi-mahi.
Fresh fish can be stored covered in your refrigerator for up to two days. If you need to store it longer, you will need to freeze it. To freeze fish, wrap tightly to prevent freezer burn. It will keep frozen for up to two months. Thaw overnight in the refrigerator before cooking. It can be thawed under cold running water if you need it sooner.
When buying fish fillets, plan on approximately 4 to 6 ounces per person.
You can substitute purchased blackening seasoning for the homemade. I like and have used Old Bay and Paul Prudhomme blends.
The cooking time shown in this recipe is for fillets that are one-half of an inch thick. If your fillets are thinner or thicker, they will take less or more time to cook properly.
If you are on a low-carb diet, eliminate or reduce the amount of brown sugar in the seasoning mix.
Leftover blackened mahi-mahi can be used to make fish cakes, fish tacos, as a topping for salads, or to make tasty fish sandwiches.

More seafood recipes:

If you are looking for other great seafood recipes, check out these favorites on my blog:

If you need more menu ideas using fish or shellfish, here is a link to all of my seafood recipes.

⭐️⭐️⭐️ ⭐️ ⭐️ If you make this recipe, please leave a comment and give it a star rating. I would love to know how you liked it!

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