Objective A California, USA, law raised the minimum tobacco sales age to 21 (T21) on 9 June 2016. We investigated whether T21 was associated with reductions adolescents’ use of tobacco cigarettes, smokeless tobacco and electronic cigarettes and whether these associations differed across racial and ethnic groups.

Methods Secondary analyses of data from 2 956 054 7th, 9th and 11th grade students who participated in the California Healthy Kids Survey from 2010–11 to 2017–2018.

Results Multilevel mixed effects logistic regression analyses showed that T21 was associated with reduced prevalence of lifetime smokeless tobacco and e-cigarette use and past month smokeless tobacco use in the overall student population. T21 was associated with increases in prevalence of past month e-cigarette use. Moderation analyses indicated differences by racial and ethnic groups. Notably, T21 was associated with reductions in lifetime and past 30-day use of all tobacco and nicotine products among Latinx youth. The findings were more mixed for other racial and ethnic groups. Slopes analyses indicated that T21 was associated with accelerated downward trends for 30-day cigarette and smokeless use; moderated trends for lifetime cigarette smoking such that downward slopes became less steep; and reversed downward trends for e-cigarette use. Changes in slopes varied across racial and ethnic groups.

Conclusions Our findings highlight the importance of understanding the complex associations that T21 and other tobacco control policies have with the use of different tobacco and nicotine products among racial and ethnic groups. Future research should investigate mechanisms underlying these differences to inform tobacco control efforts.