Preheat the oven to 350°F (175°C). Line a baking sheet with aluminum foil.
Arrange cinnamon graham crackers in a single layer on the prepared baking sheet.
Sprinkle chopped walnuts evenly over the graham crackers.
Add butter, brown sugar, and cinnamon to a saucepan over medium heat.
Bring the mixture to a boil and cook until smooth and combined.
Pour the warm butter and brown sugar mixture evenly over the graham crackers and walnuts.
Bake for about 10 minutes, until the topping is bubbly and lightly browned.
Remove from the oven and allow the bars to cool completely.
Break into pieces and serve.