Abstract Background Increasing use of substances is observed among adolescents in recent years. Early onset of substance use dramatically increases the risk of substance use disorder, dependence, and poorer psychological, social, and physical health, and is thus a public health concern. We explore trends in socioeconomic inequalities in past year use of cannabis and other illicit drugs between 2014 and 2022 among Norwegian adolescents. Methods This study is based on data retrieved from five waves of the nationwide Norwegian Ungdata survey (2014-2022) among adolescents attending upper secondary education (N = 282,259; 51 % girls). Trends in socioeconomic inequalities were assessed using the Slope Index of Inequality (SII) and the Relative Index of Inequality (RII). Results The use of cannabis and other illicit drugs increased among boys (from 13% to 19%, and from 2% to 5%, respectively) and girls (from 8% to 14%, and from 1% to 3%, respectively) between 2014 and 2022. Higher prevalence’s was observed among the least affluence girls between 2020 and 2022, both in absolute and relative terms (SII: 0.01 to 0.06, RII: 0.97 to 1.52, p < 0.001). No inequalities were observed among boys during this time. While relative and absolute inequalities in use of other illicit drugs decreased in boys, absolute inequalities increased in girls. Boys were more likely than girls to have used cannabis and other illicit drugs, although the gender gap in cannabis use narrowed slightly during the study period. Conclusions Our data suggest increasing use of cannabis and other illicit drugs among Norwegian adolescent boys and girls between 2014 and 2022. Future studies should examine the potential causes of increasing substance use as a basis for understanding, and distinguishing between, the many intertwining factors that influence adolescent drug use behaviors. Key messages • The use of cannabis and other illicit drugs increased between 2014 and 2022 among Norwegian boys and girls. • While inequalities in the use of cannabis and ither illicit drug use increased in girls, small or no inequalities was observed among boys.