Heat 1 tablespoon of olive oil in a large skillet over medium heat. Add the diced bell pepper and onion. Cook for approximately 3–4 minutes, stirring frequently, until the vegetables begin to soften while retaining some texture. Reduce the heat slightly if they brown too quickly.
Add the minced garlic to the softened vegetables. Stir continuously and cook for approximately 1 minute, until fragrant. Avoid overcooking the garlic to prevent bitterness.
Add the ground chicken to the skillet. Use a wooden spoon or spatula to break the meat into small pieces while mixing it with the vegetables. Cook for approximately 5–7 minutes, stirring occasionally, until the chicken is completely cooked through. If the mixture becomes too dry, add a small splash of water or broth.
Stir in the tomato sauce, ketchup, Worcestershire sauce, Cajun seasoning, smoked paprika, salt, and black pepper. Mix thoroughly until the chicken and vegetables are evenly coated. Reduce the heat to low or medium-low and simmer for approximately 10 minutes, stirring occasionally, until the sauce thickens and clings to the chicken. Adjust the Cajun seasoning to taste. If the mixture is too watery, simmer a little longer or use an optional cornstarch-and-water mixture to thicken it.
While the chicken filling simmers, toast the hamburger buns using a separate skillet over medium heat or a toaster. Toast until the surfaces become lightly golden and slightly crisp. This helps the buns maintain their structure when filled with the saucy chicken mixture.
Place the toasted bottom halves of the hamburger buns on serving plates. Spoon the warm chicken mixture evenly over each bun without overfilling. Add optional sliced pickles, shredded cheese, or coleslaw according to preference. Finish assembling the sandwiches while the filling is hot.
Serve the Ground Chicken Sloppy Joes immediately with your preferred side dishes, such as crispy French fries, sweet potato wedges, or a fresh green salad. For leftovers, refrigerate the filling separately from the buns in an airtight container for up to 3 days. Reheat the filling in a skillet until thoroughly heated before assembling fresh sandwiches.