When will legislators assigned to the same committee cooperate with eachother? In federal presidential regimes, both the President and governorsdemand policy answers from members of the House of Representatives andthe Senate. Legislators’ preferences sometimes coincide with those of thePresident and the governors of their home states; on other occasions, theyonly align with the preferences of the President or the state governor; and,finally, at times preferences align with neither. In this paper, I analyse thecommittee system of a multi-party and multi-level legislature and test thepartisan and territorial determinants of committee collaboration. My theoryelucidates the inner workings of committee systems with competingprincipals and multiple parties to explain why we observe more activecollaboration among supporters of the President and less active collaborationamong those only aligned with the governor or with the opposition. Iexemplify with the Argentine House of Representatives (1993–2017).