Remote work has expanded rapidly, but the value of regular in-person contact remains unclear. We report a randomized controlled trial in which a large multinational randomly assigned 248 customer-service employees to remain fully remote or to work at the office together one day a month. Monthly office days gradually increased productivity, with treated employees handling 7.8% more calls per hour in the post-intervention period. Office days also strengthened workplace communication: treated employees spent 36 additional minutes communicating with colleagues in the week after an office visit, were more likely to report receiving manager feedback, and employee pairs randomly assigned as desk neighbors were 11 percentage points more likely to communicate afterward. In addition, monthly office days reduced attrition by a third. The resulting gains in productivity and retention generated a benefit–cost ratio of about 5:1. These findings show that limited, coordinated in-person contact can improve communication, performance, and retention in remote teams.