Heat the olive oil in a large pot or Dutch oven over medium heat. Add the diced onion and cook until soft and translucent, about 5 minutes.
Stir in the minced garlic, diced bell pepper, and diced carrots. Sauté for another 5 minutes until the vegetables are tender.
Add the kidney beans, black beans, diced tomatoes (with their juice), pumpkin puree, and vegetable broth to the pot. Stir to combine.
Season the mixture with chili powder, cumin, smoked paprika, salt, and pepper. Stir well.
Bring the chili to a boil, then reduce the heat to low and let it simmer for 30 minutes, stirring occasionally.
Taste and adjust the seasonings if needed. If the chili is too thick, you can add more vegetable broth until the desired consistency is achieved.
Serve the Pumpkin Chili hot, topped with sour cream, shredded cheese, and fresh cilantro if desired.