Message factors in union marketing communications are important for improving public attitudes toward unions and facilitating union renewal. However, little is known about the prevalence of different message factors in union advertising. We conduct a content analysis of the message factors in 177 union print advertisements from three Canadian unions to determine which message factors are most commonly being employed. We then compare our findings to the techniques marketing research has found to be more or less effective when engaging in organizational marketing. We conduct the largest systematic examination of union advertising to date, and suggest that there are areas of both strength and weakness in current union print advertising. Implications of our findings for union renewal are discussed. Copyright © 2018 ASAC. Published by John Wiley & Sons, Ltd.