Purpose: According to Vygotskian theory, verbal thinking serves to guide our behavior and underpins critical self-regulatory functions. Indeed, numerous studies now link inner speech usage with performance on tests of executive function (EF). However, the selectivity of inner speech contributions to multifactorial executive planning performance and links with real-world functioning are limited. Therefore, the present study seeks to fill this gap in our knowledge. Method: Fifty-one adults completed the Tower of London under 2 conditions, (a) articulatory suppression and (b) foot tapping, and provided self-ratings of real-world executive functioning (utilizing the Behavior Rating Inventory of Executive Function-Adult Version; Roth, Isquith, & Gioia, 2006). Results: Interfering with inner speech selectively disrupted Tower of London performance over and above a simultaneous motor task (i.e., foot tapping). Furthermore, this selectivity in performance was linked with real-world self-monitoring. Conclusion: These results provide further evidence for specific links between verbal thinking and EF (particularly using multifactorial tasks of planning) and suggest that inner speech might serve as a key intervention target in clinical disorders where EF deficits are prominent.