Loneliness is a rampant and modern epidemic that affects the majority of employed adults and shows no signs of subsiding. Loneliness not only contributes to numerous health problems—including anxiety, depression, heart failure, and suicide—but can also cause greater employee stress, cynicism, distrust, and decreased job performance, as well as higher turnover and absenteeism. Loneliness-prompted absenteeism singlehandedly costs employers billions of dollars a year in lost productivity. Consequently, understanding and managing workplace loneliness is of paramount importance for leaders. A review of the causes and outcomes associated with workplace loneliness is provided in this article, as well as three evidence-based interventions that can help reduce workplace loneliness: (1) fostering opportunities for relationship building, (2) increasing support around evolving work contexts, and (3) fortifying a people-focused organizational culture. By presenting research-based guidance, we help leaders combat on-the-job loneliness faced by employees, as well as managers; generate healthier work environments; and cultivate improved individual, team, and organizational performance.