Previous studies had no consensus on whether a ‘mandate-divide’ exists between district and party-list legislators under the mixed-member system. I argued that previous studies ignored the role of the party. This article aims to explore the legislative consequences of the 2005 electoral reform and the role of parties in Taiwan. I analyzed the roll-call votes, considering abstention and absence as potential defection, along with interviews. The data cover from the fifth to eighth Legislative Yuan, two periods each before and after the electoral reform. The findings show that district legislators tended to defect from the party line than list proportional representation (PR) members in pre- and post-reform periods. However, district legislators only tended to be absent from the voting than list PR members after the electoral reform. Mandate-divide was present throughout the period, but differences were more salient before the reform. Besides, evidence stressing the influence of parties was revealed in the interviews. Party leaders enforce various punishments to enforce party discipline. The role of party became more important after the electoral reform. District legislators have higher absence rate after the electoral reform because they need to engage more in constituency service or avoid expressing their position on controversial issues. The ruling party tends to sanction the absence when they have majority in parliament.