In a large pot of boiling salted water, cook the fettuccine pasta according to package instructions until al dente. Reserve ½ cup of pasta water and then drain the pasta.
In a bowl, toss the shrimp with Cajun seasoning until well coated.
In a large skillet, heat 2 tablespoons of olive oil over medium-high heat. Add the seasoned shrimp and cook for about 2-3 minutes per side until the shrimp turn pink and opaque. Remove from the skillet and set aside.
In the same skillet, add the remaining tablespoon of olive oil. Add minced garlic and sauté for about 1 minute until fragrant. Pour in the heavy cream and bring to a simmer.
Gradually whisk in the Parmesan cheese until smooth. Add the chopped spinach and stir until wilted.
Return the cooked shrimp to the skillet. Add the drained fettuccine, tossing to coat with the creamy sauce. If the sauce is too thick, add reserved pasta water a little at a time until desired consistency is reached.
Taste and season with salt and pepper as needed.
Divide the Cajun shrimp Alfredo into bowls and garnish with fresh parsley.