Heat olive oil in a large pot over medium heat.
Add the chopped onion, bell pepper, and celery; sauté until softened.
Stir in the minced garlic and cook for an additional minute.
Add the diced chicken breast and cook until browned.
Mix in the sliced sausage and cook until heated through.
Pour in the diced tomatoes and chicken broth; stir well.
Add Cajun seasoning, salt, and pepper to taste.
Bring the mixture to a boil, then stir in the rice.
Reduce heat to low, cover, and simmer for 20 minutes.
After 20 minutes, add the shrimp and cook for an additional 5 minutes, until shrimp are cooked through.