How do electoral rules affect the occurrence of legislative party switching? Existing research addressing this question is limited and does not reach a consistent conclusion. This article argues that electoral systems that encourage politicians to cultivate a personal vote dampen parties’ ability to retain members. The greater incentives to cultivate a personal vote in candidate-centred electoral systems result in politicians relying more on local supporters and less on party label for their re-election. In such systems, compared to party-centred systems, I expect that only parties that suffer electoral setbacks to be more likely to witness switching, as their candidates are less concerned with party labels, and local supporters might follow them to the new party, thus reducing switching costs. Drawing on data from 17 European democracies over the period 1990–2013, I find support for my hypothesis. While there is no direct effect of electoral rules on switching, the results suggest that this effect hinges upon parties’ ability to deliver seats: losing parties are more likely to witness switching in candidate-centred systems than in party-centred systems. Further findings also demonstrate how this effect is especially significant when district magnitude is large and the next election is approaching.