Spray a large metal mixing bowl and a wooden spoon with non-stick spray. Add the popcorn and pecans to the bowl and toss together.
In a small non-stick saucepan over medium heat, add the butter, syrup, and salt. Bring to a boil and cook until the mixture registers 300 degrees F on a candy thermometer.
Pour the hot caramel over the popcorn and pecans and use the wooden spoon to stir quickly until the everything is nicely coated. Immediately spread the mixture out onto a large baking sheet and allow to cool completely. Break the popcorn into smaller pieces and serve or store in an airtight container or bag.