Salespersons are increasingly expected to explore cross-/up-selling opportunities while simultaneously fulfilling customer service requests; an activity known as service-sales ambidexterity. Engaging simultaneously in these seemingly conflicting tasks may pose self-regulatory and motivational challenges for salespersons. Drawing from regulatory mode and self-determination theories, this study argues that salespersons' engagement in service-sales ambidexterity is driven by the 'can do' motivations of locomotion and assessment orientations, and the 'reason to' motivations of enjoyment of work and driven to work. This study contributes to the new literature stream on service-sales ambidexterity by testing a model that integrates the two behavioral motivation explanations. Results indicate that service-sales ambidexterity is jointly determined by the 'can do' and the 'reason to' motivations, both directly and through their interactions. The study offers new theoretical and managerial implications on ambidexterity at the individual level of analysis.