Do interpersonal relationships among and between representatives and senators affect legislative collaboration in the contemporary Congress? The extant literature on Congress suggests interpersonal dimensions of life on Capitol Hill should play a minimal role in the legislative process. However, research in other fields, including psychology, finds that relationships are crucially important within organizations. In addition, many contemporary accounts of congressional deal‐making highlight the role of personal relationships. Drawing on interviews with high‐level congressional staff, and data on CODEL trips taken by members of Congress, we show that interpersonal relationships help promote collaboration across the aisle. These findings have implications for how we understand the contours of conflict and cooperation on Capitol Hill. [ABSTRACT FROM AUTHOR]