Preheat the oven to 350°F.
In a medium bowl, combine crushed pretzels, granulated sugar, and melted butter. Mix until well combined.
Press the mixture firmly into the bottom of a 9x13-inch baking dish.
Bake for 10 minutes, then remove from the oven and let cool completely.
In a large mixing bowl, beat the softened cream cheese and powdered sugar together until smooth.
Gently fold in the whipped topping until fully incorporated.
Spread the cream cheese mixture evenly over the cooled pretzel crust.
In another bowl, dissolve the berry-flavored gelatin in 2 cups of boiling water, stirring until fully dissolved.
Allow the gelatin to cool slightly, then add the mixed berries.
Pour the berry mixture over the cream cheese layer in the baking dish.
Refrigerate for at least 4 hours or until set.
Cut into squares and serve chilled.
