Once in office, women politicians are less likely to seek re-election. Yet, the causes and potential remedies for this gender gap in political retention are still poorly understood. We argue that women politicians are more likely to feel isolated and to lack the necessary support networks to navigate the challenges of holding public office. In a field experiment with a civil society organization, we test whether inviting women councillors in the UK to join a real cross-partisan support network of women councillors reduces the gender gap in political retention. We find that women councillors invited to join the peer support network are 10 percentage points more likely to express interest in running for re-election. Semi-structured interviews suggest that this effect is driven in part by shaping perceptions of isolation in office and peer support. The effects do not spillover to progressive political ambition. The study reveals that efforts to promote women’s representation would benefit from focusing not only on selection but also on retention of women in politics.