Preheat an oven to 400 degrees F (200 degrees C). Spray a shallow baking dish with nonstick cooking spray.
Pat mahi mahi dry with paper towels. Drizzle with sesame oil, and season with garlic pepper. Press grated ginger and toasted sesame seeds onto both sides of the fish to coat. Place fish on the prepared baking dish.
Bake in the preheated oven until the fish flakes easily with a fork, 10 to 15 minutes.