In most bicameral systems, both legislative chambers must agree on a bill before it may become law. In the United States Congress, agreement often comes during negotiations which occur after each chamber has passed an initial version of the bill. Our understanding of the post-passage resolution process is very limited and has traditionally been limited to question of “who wins” in conference committees. The post-passage bargaining process is more complex and more important than this work suggests. For example, it is not well understood why the House and Senate must sometimes bargain and why they can sometimes agree on legislation without having to bargain and why the two chambers sometimes use conference committees to settle their differences but other times use the amendment trading process. Likewise, the relationship between post-passage bargaining and policy outcomes or legislative productivity is more nuanced than current literature on parties and member preferences suggests. In this dissertation, I take the strategic interaction of the coalitions in each chamber seriously by treating them as two actors pursuing electoral and policy goals within the constraints of the institution. I use a noncooperative bargaining model to find the conditions under which post-passage bargaining occurs, why chambers choose between a conference committee and amendment trading, why the chambers sometimes fail to reach agreement, the ways in which bicameral bargaining can increase legislative productivity even when the chambers are controlled by different parties, and how post-passage bargaining affects policy. Each chamber faces a risk-return tradeoff during the passage and post-passage bargaining stages, and it is this tradeoff which leads to successful reconciliation or failure. The results have implications not just for post-passage bargaining, but also for theories of legislative organization, coalition building within Congress, and the effect of partisanship on institutional procedures and outcomes.