In a large bowl, mix together the popcorn and pecans.
To a large saucepan over medium-high heat, add brown sugar, corn syrup, and butter. Bring to a boil and stir occasionally.
Once boiling, remove from heat and stir in vanilla and baking soda.
Pour over popcorn and pecans and toss to coat.
Transfer mixture to a large rimmed sheet pan and spread out evenly. Bake 30-40 minutes, stirring every 10 minutes. Immediately spread out onto foil or parchment paper to cool. Once cool, break apart and serve. Enjoy!