Cook the fettuccine according to package instructions until al dente. Drain and set aside.
In a large skillet, heat the olive oil over medium heat. Add the shrimp and cook for about 2-3 minutes on each side until pink and opaque. Remove the shrimp from the skillet and set aside.
In the same skillet, add the minced garlic and sauté for about 1 minute until fragrant. Stir in the Cajun seasoning, salt, and black pepper.
Pour in the heavy cream and bring to a gentle simmer. Stir in the Parmesan cheese until melted and smooth.
Add the cooked fettuccine, shrimp, and crab meat to the skillet. Toss to combine and heat through for about 2-3 minutes.
Remove from heat and stir in the chopped parsley and lemon juice. Serve immediately.