Horizontal accountability, in which institutional actors with equivalent levels of authority possess tools to challenge one another, is a critical component of mature and stable democracy. This article investigates ways in which partisanship differentiates how political actors use a specific accountability tool – legislative questions – and the responsiveness of government institutions to inquiries. We take advantage of the unanticipated change in Ukraine's executive leadership in 2004 to assess the relationship between partisan identity and accountability. The analysis of nearly 16,000 legislative requests from Ukraine illustrates the pivotal role of partisanship in accountability and institutional responsiveness, a finding that is particularly notable given Ukraine's inchoate party system and under-developed democratic norms.