Employer monitoring of employees’ and job applicants’ social networking site (SNS) data is widespread and growing, but remains ethically, legally and efficaciously controversial. Examining this emergent source of tension in the employment relationship, this paper explores how Generation Y employees experience and perceive employer use and monitoring of SNSs, and whether employer‐related concerns influenced their online behaviour. A survey of 385 employed students revealed widespread SNS engagement amongst respondents, with many experiencing some form of employer SNS use. Employer SNS use was, however, generally perceived negatively. Negativity took the form of procedural justice violations based on issues such as invasion of privacy. Nevertheless, many students displayed alertness through actively managing online profiles which, in turn, marginally yet significantly increased their justice perceptions. The study has ethical and practical implications for employer monitoring and use of SNSs, as well as contributing to our understanding of young people's online behaviour.