Blackened Mahi Mahi Fish Sandwich

Name: Blackened Mahi Mahi Fish Sandwich Recipe
Prep time: 10 min
Cook time: 10 min
Total time: 20 min
Ingredients: 4 (6-ounce) Mahi Mahi fish filets; 2-3 tablespoons olive oil; 1 recipe Blackened Seasoning Spice Rub ((See recipe below)); 4 Hamburger buns; lettuce; tomato (sliced); red onion (sliced); 1 recipe Tartar sauce ((See Recipe below)); For serving: fries ((chips or coleslaw, lemon wedges, pickle spears)); 2 teaspoons smoked paprika; 1 teaspoon chili powder; 1/2 teaspoon garlic powder; 1/2 teaspoon onion powder; 1/2 teaspoon cumin; 1/2 teaspoon salt; 1/4 teaspoon black pepper; 1 cup mayo; 2 tablespoon fresh dill (chopped); 2 tablespoons dill relish; 2 teaspoons shredded onion; 1 teaspoon lemon juice

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Looking for a fish sandwich that's packed with flavor, easy to make, and feels like a mini vacation on a plate? You've gotta try this Blackened Mahi Mahi Fish Sandwich recipe.

Imagine flaky, firm mahi mahi fillets coated in a smoky, spicy seasoning, seared to perfection, and nestled on a toasted bun with crisp veggies and a zesty homemade tartar sauce.

Side view of Blackened Mahi Mahi Fish Sandwich with a bite taken out of it with green leaf lettuce, red onions and homemade tartar sauce.

If you loved my Grilled Mahi Mahi Recipe, and Blackened Salmon Recipe, this recipe will likely become one of your favorite Seafood Recipes!

Why You'll Love This Recipe

Quick: With only 10 minutes of prep and 10 minutes of cook time, you've got a delicious homemade dinner for four.
Unique Flavor: The homemade Spice Rub is a Cajun seasoning-inspired blackened seasoning mix with a little Mexican flavor added. What makes this recipe unique is the addition of cumin to the traditional Cajun Blackening seasoning.
Homemade Tartar Sauce: Instead of store-bought tartar sauce, this includes an easy recipe for a fresh, vibrant, homemade tartar sauce with fresh dill.
Versatile: Serve it with crispy french fries, Sweet Potato Fries, Sweet Potato Chips, Tortilla Chips, or Coleslaw, like my Cajun Honey Jalapeno Slaw, and you've got a meal that feels indulgent but is secretly pretty wholesome.

Open Blackened Mahi Mahi Fish Sandwich topped with homemade tartar sauce with green lettuce, slice of tomato, and red onion served with sweet potato fries and sliced lemon.

Featured Ingredients and Substitutions

See the printable recipe card at the bottom of this post for the complete ingredient list with quantities.

Overhead view of each of the ingredients for Mahi Mahi Fish Sandwiches with blue labels and ingredient names in white text

Mahi Mahi Fillets: The star of the show! These 6-ounce beauties have a firm flesh that holds up to blackening like a champ. No mahi mahi at your local grocery store? Swap in another white fish like cod, tilapia, or halibut-they'll work just fine.
Blackened Seasonings: We're mixing smoked paprika, chili powder, garlic powder, onion powder, cumin, salt, and black pepper for that bold, smoky crust. Feel free to use a store-bought cajun seasoning if you're short on time.
Olive Oil: A few tablespoons help get that perfect sear in a large non-stick pan or cast-iron skillet. You could sub in avocado oil if that's your vibe.
Hamburger Buns: Simple and classic, but a toasted brioche bun or kaiser roll takes it up a notch. Want a hoagie vibe? Go for a hoagie roll instead!
Toppings: Fresh green leaf lettuce, or shredded lettuce, tomato slices, and red onions add crunch and sweetness. Mix it up with avocado or pickles if you're feeling fancy.
Tartar Sauce: Mayo, fresh dill, dill relish, shredded onion, and lemon juice make a creamy, tangy sauce that's pure gold. Store-bought works too if you're in a pinch.

These ingredients are easy to find, and substitutions make this recipe super flexible for whatever you've got on hand!

How To Make This Mahi Mahi Fish Sandwich Recipe

See the printable recipe card at the bottom of this post for the complete instructions with ingredient list with quantities.

Make the Spice Rub: Grab a small bowl and toss in 2 teaspoons smoked paprika, 1 teaspoon chili powder, ½ teaspoon garlic powder, ½ teaspoon onion powder, ½ teaspoon cumin, ½ teaspoon salt, and ¼ teaspoon black pepper. Give it a good stir-this is your ticket to blackened perfection.

First process photo for Mahi Mahi Fish Sandwich. Overhead view of a small white scalloped bowl with a homemade Cajun Blackened Seasoning Mix with cumin and chili powder added.

Season the Fish: Pat your 4 mahi mahi fillets dry with a paper towel (key for that crispy crust!). Rub the spice mix all over both sides, pressing gently so it sticks.

2nd process photo for Mahi Mahi Fish Sandwich with overhead view of a black plate with uncooked Mahi Mahi fish filets, a small white bowl with the spice mix, and a white scalloped plate with one uncooked fish filet with the spice mix rubbed on it.

Heat the Pan: Pour 2-3 tablespoons of olive oil into a large non-stick pan or cast-iron skillet and heat it over medium heat until it's shimmering-hot but not smoking.

Third process photo showing overhead view of uncooked blackened mahi mahi filets in black cast iron skillet.

Cook the Fish: Add the fillets to the hot pan and let them sizzle for about 4 minutes on the first side. Flip 'em and cook for another 3-4 minutes, until they're opaque and flake easily with a fork. (Pro tip: aim for a minimum internal temperature of 145°F if you're using a thermometer.) Let them rest for a minute off the heat.

Fourth process photo showing overhead view of cooked blackened mahi mahi filets in a hot black cast iron skillet.

Prepare the Tartar Sauce: In a mixing bowl, combine 1 cup mayo, 2 tablespoons chopped fresh dill, 2 tablespoons dill relish, 2 teaspoons shredded onion, and 1 teaspoon lemon juice. Stir it up and pop it in the fridge until you're ready to assemble.

Fifth process photo. Overhead view of small bowl with ingredients for homemade tartar sauce, including mayonnaise, fresh dill, and dill relish.

Assemble the Sandwich: Toast your hamburger buns if you're into that (who isn't?). Layer the bottom bun with shredded lettuce, tomato slices, red onions, and a juicy mahi mahi fillet. Slather a generous dollop of tartar sauceon the fish, then cap it with the top bun.

6th process photo of Blackened Mahi Mahi Fish Sandwich showing the prepared ingredients just before assembling sandwiches. One plate with the fish filets with a slice of green lettuce, one bowl of tartar sauce, one plate with hamburger buns, one plate with sliced tomatoes and sliced red onions, and a plate with green lettuce and pickle slices.

Serve: Plate it up with french fries, chips, or coleslaw, plus lemon wedges and pickle spears on the side. Bon appétit-you've just made one of the best fish sandwiches ever!

Recipe Tips

Room Temp Fish: Pull those mahi mahi fillets out of the fridge 30 minutes before cooking. Cold fish cooks unevenly and can dry out-nobody wants that!
Fresh Fish is Best: Go for fresh fish or properly thawed fillets. Look for firm, moist mahi mahi with a mild scent at your local grocery store.
Dry It Right: Use a paper towel to pat the fillets dry before seasoning-it helps the blackened seasonings stick and crisps up the outside.
Spice It Up: Don't skimp on the spice rub! Coat every inch for that bold, smoky flavor that makes this a true blackened mahi-mahi sandwich.
Hot Pan, Happy Fish: Preheat your skillet properly over medium heat. A hot pan = a killer sear and crust. Cast-iron is your best friend here.
Don't Overcook: Mahi mahi cooks fast-4 minutes one side, 3-4 minutes the other. Overdo it, and it'll turn tough. Watch the fish thickness and flake it with a fork to check.
Topping Freedom: Stick with lettuce, tomato, and red onions, or get wild with avocado, spicy slaw, or even a fried egg if you're feeling extra.
Serve Fresh: Assemble and eat right away for the crispiest, tastiest sandwich. No soggy buns allowed!

Overhead view of an open faced Blackened Mahi Mahi Fish Sandwich on a plate served with homemade tartar sauce, sweet potato fries and a pickle sliced vertically.

Variations

Want to switch it up? Here's how to remix this fish sandwich recipe:

Air Fryer Vibes: Skip the skillet and cook the seasoned fillets in an air fryer at 400°F for 8-10 minutes. Crispy without the oil!
Brioche Bliss: Swap the hamburger buns for brioche buns or a toasted brioche bun for a buttery, sweet twist.
Spicy Kick: Add cayenne to the spice rub or drizzle hot sauce on top if you love heat.
Taco Time: Ditch the bun and tuck the blackened mahi mahi into tortillas with slaw and tartar sauce for a fish taco vibe.
Side Swap: Pair it with roasted place potatoes instead of french fries for a healthier twist-toss 'em with olive oiland a pinch of salt and bake in a hot oven.

FAQs

When is Mahi Mahi Done?

Check for flakiness with a fork-it should pull apart easily. Or use a thermometer; the minimum internal temperature should hit 145°F at the thickest part.

Can I Use Frozen Mahi Mahi Fillets?

Yes! Thaw them in the fridge overnight or in cold water for a quicker fix. Just pat 'em dry with a paper towel before seasoning.

What If I Don’t Have All The Spices?

No stress-use a premade cajun seasoning or whatever you've got in the pantry. Paprika and black pepper are must-haves for that blackened vibe.

Can I Make This For A Crowd?

Absolutely, Double the recipe and cook in batches. Keep the cooked fillets warm in a hot oven (200°F) while you finish up.

How Do I Store Leftover Mahi Mahi?

Store cooked mahi mahi in an airtight container in the fridge for up to 2 days. Reheat in an air fryer or oven to keep it crispy, then assemble fresh.

Can I Freeze Leftover Mahi Mahi?

Yes. Wrap the filets tightly in plastic wrap and place in a freezer-safe, airtight container or bag for up to 3 months.

How Do I Reheat Mahi Mahi?

To reheat blackened Mahi Mahi fillets, place them on a baking sheet, cover with foil, and reheat in a preheated oven at a low temperature (around 275°F) for about 10-15 minutes.

Overhead view of a close up of the open faced Blackened mahi mahi fish sandwich topped with homemade tartar sauce.

More Seafood Recipes

There you have it-a blackened mahi mahi sandwich that's easy, flavorful, and perfect for any night of the week. Try it, and let me know how it goes! Happy cooking!