Easy Keto Diet Recipe: Delicious and Healthy Grilled Tuna Steak

Keto-Friendly Grilled Tuna Steak – Holidays on a Plate!

There are few dishes for me that conjure up beach holidays, the mediterrannean, dockside tavernas, like grilled tuna steak. Easily keto friendly, just a little bit luxurious, and if done right, once of the tastiest fish dishes you can easily make at home.

Tuna is fantastic for the keto diet as it’s got a good balance of high-quality protein, as well as plenty of essential fats including omega 3 and 6’s.  Naturally low in carbs (as all fish is really!) – it’s hard to go wrong adding some tuna into your diet, either tinned or fresh.

Succulent Grilled Tuna Steak


The Heart of the Sea on Your Plate

For me grilled tuna conjures up my memories of Greece (Corfu to be exact), my first holiday that I ate fish! I’d been a massive picky eater before then, but was convinced into trying tuna steak, and never looked back! You’d see fishermen coming into the dock, fresh tuna on their boats amongst a plethora of seafood. Tavernas by the dock serving up freshly grilled steaks, simply dressed – heaven.


This recipe is all about just complementing the tuna and letting it’s flavor sing (all while keeping it keto of course!) – We’re using just a few simple ingredients: olive oil (extra virgin of course!) for even more healthy fats. Fresh lemon juice, which always goes so well with fish; garlic and herbs for aroma and depth.

Keto Tuna Steak Preparation


Perfecting the Grilled Tuna Steak

Getting this recipe right isn’t about those other ingredients though, it’s the method and technique that will make or break your tuna. Really we’re just trying to sear the outside of the flesh as quickly and deeply as possible, without overcooking the meat and ending up with a crumbly, tough steak,

First and foremost don’t let your steak touch the grill until that grill is super hot – something like 400°F. This is crucial to get a good sear quickly for the smoky deep flavor on the surface we’re after. We want the steak to be cooked medium-rare, with good colour in the center still to make sure it’s still juicy and tender. 


We’re going to marinate the fish first briefly, just to infuse the aromatic flavors into the surface. Make sure each steak is well coated and leave for just 5 minutes or so, no need to go longer. We want the flavors to meld but don’t want to start changing the texture of the fish from long marination. 

My pro tip for an extra flavor boost is to add a sprig of rosemary to the grill while cooking. The smoke from the rosemary infuses the tuna with a subtle woody aroma that’s simply divine. And for those who love a bit of heat,  feel free to be generous with some red pepper flakes. It’s all about personalizing the dish to your palate while keeping it keto-friendly, but remember this dish is all about the tuna! Don’t go smothering it all in hot sauce or anything!

Grilled Tuna Steak Ready to Serve

Variations to the Grilled Tuna Steak

Cajun-Style Tuna Steak

Spice things up with a Cajun seasoning blend. The smoky and spicy flavor can go great with tuna, all while keeping it low-carb.

Mediterranean Tuna Steak

Top your grilled tuna with a mix of diced olives, feta cheese, and cucumbers for a Mediterranean flair, essentially a greek salad! (or just have one on the side haha). The salty olives and feta go great with tuna , the slight zing from feta is great with fatty fish.

Substitutions for Your Keto Grilled Tuna Steak

If olive oil isn’t your thing, avocado oil is a great substitute that offers a similar profile of healthy fats and a high smoke point, perfect for grilling. For those who can’t find fresh tuna, salmon steaks make an excellent alternative, with omega-3 fatty acids essential for a keto diet. 

Frequently Asked Questions

Can I use frozen tuna steaks for this recipe?
Yes, frozen tuna steaks can be used, but ensure they are fully thawed and patted dry before marinating to achieve the best flavor and texture.

How do I know when my tuna steak is done?
A medium-rare tuna steak will have a slightly pink center. It’s done when the outside is well-seared, and the inside remains tender, typically after 3 minutes per side on a hot grill.

What sides pair well with grilled tuna steak?
Keto-friendly sides like sautéed spinach, cauliflower rice, or a fresh arugula salad complement the richness of the tuna steak.

How long can I marinate the tuna steaks?
For top results, marinate at least 5 minutes and up to 30 minutes. Don’t marinate too long as the lemon juice acidity can start to “cook” the fish.

Can I grill the tuna steak indoors?
Yes, a grill pan on the stove works. Make sure it’s very hot before adding the tuna steaks to copy the high heat of an outdoor grill.

Succulent Grilled Tuna Steak

Indulge in a succulent grilled tuna steak, seasoned with a harmonious blend of herbs and spices, seared to perfection. This keto-friendly recipe offers a perfect balance of protein and healthy fats, ideal for a satisfying lunch or dinner.
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Prep Time 10 minutes
Cook Time 6 minutes
Total Time 16 minutes
Course Dinner
Cuisine American
Servings 2 servings
Calories 310 kcal


  • Grill
  • Small bowl
  • Whisk
  • Shallow dish
  • Tongs


  • 2 Tuna steaks each 6 ounces or 170 grams
  • 2 tbsp Olive oil
  • 1 tbsp Fresh lemon juice
  • 2 cloves Garlic, minced
  • 1 tbsp Fresh parsley, chopped
  • 1 tsp Dried oregano
  • ½ tsp Salt
  • ¼ tsp Ground black pepper
  • ¼ tsp Crushed red pepper flakes optional


  • Preheat your grill to high heat, approximately 400°F (204°C).
  • In a small bowl, whisk together olive oil, lemon juice, minced garlic, chopped parsley, oregano, salt, black pepper, and red pepper flakes (if using) to create the marinade.
  • Place the tuna steaks in a shallow dish and pour the marinade over them, ensuring both sides are well-coated. Let the steaks marinate for 5 minutes.
  • Once the grill is hot, oil the grill grates to prevent sticking. Place the marinated tuna steaks on the grill.
  • Grill the tuna steaks for about 3 minutes on each side for medium-rare, or longer if you prefer more well-done fish.
  • Remove the tuna steaks from the grill and let them rest for a couple of minutes before serving.


Tuna steak is best enjoyed medium-rare to preserve its moisture and flavor. If overcooked, it can become dry and tough.
Always ensure your grill is hot before cooking to get a good sear on the steaks.
Feel free to adjust the level of heat by increasing or decreasing the amount of red pepper flakes.


Calories: 310kcalCarbohydrates: 1gProtein: 44gFat: 14gFiber: 0.2gNet Carbs: 0.8g
Keyword Grilled Tuna Steak, Healthy Seafood Recipe, Keto Tuna Steak, Low Carb Grilled Fish
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