We examine the effects of a major pension reform in 2015 on the joint retirement decisions of working couples in the Netherlands. The reform abolished the partner allowance, a state pension supplement for a nonworking partner below the state pension age. At the same time, actuarially generous early retirement arrangements were made less attractive. Using rich administrative data, we estimate a multivariate mixed proportional hazards model that distinguishes between several sources of joint retirement: financial incentives, other causal mecha nisms that make retirement of one spouse more likely when the other spouse retires (e.g., due to complemen tarities in leisure or social norms) and correlated preferences (observed and unobserved heterogeneity). We find that, conditional on observed and unobserved characteristics, the reform reduced the tendency to retire jointly and argue that this is not only due to a change in financial incentives but also to a change in the social norm.