Salespeople play a crucial role in their firms’ efforts to provide customer solutions. However, little research has examined how salesperson involvement in customer solutions can be conceptualized, whether it pays off, and what boundary conditions might heighten its performance effects. This study addresses these gaps and offers a conceptualization of salesperson solution involvement by focusing on the set of salesperson-related activities that enact the four relational processes inherent in customer solutions. The authors collect a unique data set that includes a wide range of firms, industries, and countries, as well as the perspectives of both salespeople and customers, across five studies. Results validate the stability of the conceptualization across contexts. They also reveal that salesperson solution involvement is systematically related to increases in both subjective and objective, time-lagged measures of sales performance. Finally, results show that the performance effects of salesperson solution involvement are amplified under higher levels of firm's product portfolio scope, sales unit cross-functional cooperation, and customer–supplier relationship tie strength. Surprisingly, customer adaptiveness is not found to moderate the performance effects of salesperson solution involvement.