In a large skillet over medium-high heat, brown the ground turkey with the diced onion and minced garlic until the turkey is cooked through and no longer pink, about 8-10 minutes. Drain any excess fat.
Transfer the cooked turkey mixture to your slow cooker.
Add the pumpkin puree, kidney beans, diced tomatoes, chicken broth, chili powder, cumin, cinnamon, salt, and pepper to the slow cooker. Stir everything together until well combined.
Cover and cook on low for 6-7 hours or on high for 3-4 hours.
Taste and adjust seasonings as needed before serving. Top with your favorite chili toppings like sour cream, shredded cheese, green onions, or tortilla chips.