Career readiness is an important short-term outcome of career guidance activities in England. This research (1) details the development of a career readiness measure and (2) tests the relationship between career guidance interventions and career readiness among secondary school students. The measure was piloted on pupils (Study 1, N = 1508) in England taking part in a career guidance pilot programme. The instrument fitted a nine-item one-factor structure. In Study 2 (N = 2240), we found further evidence the factor structure was a good fit to the data. In Study 3 (N = 5242), we tested the relationship between career guidance activities and career readiness. Greater participation in career guidance activities was significantly associated with increased career readiness. These findings have implications for policymakers and researchers.