Peers may help others avoid violating organisational information security policies (ISPs). This study explores how peer monitoring reduces employee ISP violation intention. We propose that peer monitoring discourages employees from violating ISP. Moreover, trust plays an important role. Trust not only facilitates peer monitoring, but also moderates the effect of peer monitoring on employee ISP violation intention. In addition, collective responsibility leads to peer monitoring. We test our research model with data from two waves of surveys of 254 employees in the United States conducted two weeks apart. We utilise four scenarios in the second wave of surveys capturing the dependent variable and measure all other constructs in the first wave of surveys. Our results suggest that peer monitoring decreases one's intention to violate ISPs. Furthermore, both collective responsibility and trust contribute to peer monitoring. Finally, trust amplifies the effect of peer monitoring on employees' intention to violate ISPs. We discuss the theoretical contributions and practical implications.