Heat olive oil in a skillet over medium-high heat. Once warm add in onion, green pepper, and celery, sauté until soft, 4-5 minutes. Add in garlic and sauté for another 1-2 minutes until fragrant. Season with salt, pepper, cayenne, garlic powder, onion powder, thyme, and oregano.
Add in ground chicken and sauté until cooked through. Add in ketchup and mix to combine.
Serve on a toasted bun and enjoy immediately. Leftover sloppy joe mix will keep in an airtight container for 3-4 days.