Place the cream cheese, pumpkin puree, granulated sugar, pumpkin pie spice, and vanilla extract in a mixing bowl. Beat with an electric mixer until the mixture is smooth and fully combined.
In a separate bowl, combine the heavy cream and powdered sugar. Whip until stiff peaks form.
Fold the whipped cream into the pumpkin mixture using a spatula until no white streaks remain and the mousse looks light.
Spoon the mousse into the graham cracker crust and spread it evenly with the spatula.
Cover the pie and refrigerate for at least 4 hours until the mousse firms up.
Sprinkle ground cinnamon over the top just before slicing and serving.