Use paper towels to pat the mahi mahi fillets dry.
Sprinkle the top and bottom of the mahi mahi with salt and pepper.
Add the oil to a large skillet over medium-high heat. Once hot, carefully add each fillet to the skillet. Let the fish cook until the side touching the bottom of the pan is a beautiful golden color, about 4 to 5 minutes depending on the size of the fillets.
Carefully flip the mahi mahi. Reduce the heat to medium-low. Add the butter, lemon juice, and garlic. Give the sauce a stir so that it's combined. Cover and let the mahi mahi cook until it flakes easily with a fork, 3 to 4 minutes.
Remove the skillet from the heat. Stir the parsley into the sauce and spoon the sauce over the mahi mahi.