Nurses are increasingly providing primary care, yet the literature on cost-sharing has paid little attention to nurse visits. We employ a staggered difference-in-differences design to examine the effects of adopting a 10-euro copayment for nurse visits on the use of public primary care among Finnish adults. We find that the copayment reduced nurse visits by 9%–10% during a one-year follow-up. There is heterogeneity by income in absolute terms, but not in relative terms. The spillover effects on general practitioner (GP) use are negative but small, with varying statistical significance. We also analyze the subsequent nationwide abolition of the copayment. However, we refrain from drawing causal conclusions from this due to the lack of credibility in the parallel trends assumption. Overall, our analysis suggests that moderate copayments can create a greater barrier to access for low-income individuals. We also provide an example of using a pre-analysis plan for retrospective observational data.