Add the oats, flaxseed, pumpkin pie spice, cinnamon, and salt to a large mixing bowl.
Stir in the pumpkin puree, nut butter, maple syrup, and vanilla extract.
Mix until everything is evenly combined.
Fold in the mini chocolate chips if using.
Chill the mixture for 20 minutes if it feels too soft.
Scoop about 1 tablespoon of mixture and roll into balls.
Place the energy balls on a lined tray or plate.
Refrigerate for at least 30 minutes before serving.
Store in an airtight container in the refrigerator for up to one week.