Background Little is known about community mental health service use prior to offending. Aim This study aimed to investigate the 1‐year community mental health service use by adult offenders (18–44 years) prior to their first ever criminal sentence in Western Australia. Methods Administrative mental health service data were compared between all offenders (n = 23,755) commencing their first ever criminal sentence in Western Australia during 1985–1994 and a matched community group of 21,977 non‐offenders. Results Just over 8% of offenders had used mental health services prior to sentence compared with 1% of non‐offenders. After adjusting for age, offenders were more likely to have used these services than non‐offenders in all gender–race groups, but the effect was strongest for non‐Indigenous women, who were over 12 times more likely to have used such services, and weakest among Indigenous men, who were about twice as likely to have used them as their non‐offending peers. Service use for substance use disorder, the most common diagnosis, was about one and a half times more prevalent among Indigenous than non‐Indigenous offenders, regardless of gender. For non‐Indigenous offenders, prevalence of any mental health service contact was higher for violent than non‐violent offenders, irrespective of gender. Service use was no different between offenders receiving custodial or non‐custodial sentences in all gender‐race groups. Conclusion The higher likelihood of mental health service use by offenders in the year prior to their first ever sentence than by non‐offenders suggests that, insofar as the disorder was relevant to offending, there were some opportunities for preventive measures during that time. Differential service use according to gender and Indigenous/non‐Indigenous status is of concern. It would be important to understand more about this apparently unequal service access, not least because Indigenous populations tend to be over‐represented in prison. Copyright © 2014 John Wiley & Sons, Ltd.