Bring a large pot of salted water to a boil and cook the spaghetti until al dente, about 8–10 minutes.
Drain and set aside, keeping ½ cup of pasta water.
In a large skillet, heat olive oil over medium-high heat.
Add diced chicken and cook for 6–8 minutes until browned and cooked through.
Stir in minced garlic and Cajun seasoning, cooking for about a minute until fragrant.
Reduce the heat and pour in heavy cream, then stir in Parmesan until melted and smooth.
Add the spaghetti and toss until coated, using a splash of pasta water if needed.
Season with salt and pepper, garnish with fresh parsley, and serve warm with garlic bread or a crisp salad.