Whisk flour, brown sugar, baking powder, baking soda, salt, pumpkin pie spice, and cinnamon in a large bowl.
In a separate bowl, whisk milk, pumpkin puree, egg, and vanilla until smooth. Stream in melted butter while whisking.
Pour wet ingredients into the dry. Stir gently until just combined; a few small lumps are fine. Rest 5 minutes.
Heat a lightly oiled griddle or skillet over medium. When a drop of water sizzles, it’s ready.
Scoop about 1/4 cup batter per pancake. Cook until bubbles set around edges, 2–3 minutes.
Flip and cook until golden and cooked through, 1–2 minutes more. Repeat with remaining batter.