Abstract Background Sexual identity, linked to experiences of disadvantage and discrimination, is crucial in equality monitoring. Sweden’s gender-neutral marriage laws, introduced in 2009, provide a unique context. This study examines the population trends and demographic disparities in sexual identity over time. Methods We analyzed three population surveys (2010, 2014, 2021) from the Stockholm Public Health Cohort, including around 50,000 individuals per survey. Sexual identity was assessed via self-administered questionnaires. Demographic data were sourced from Swedish national registers. Weighted multivariate Poisson regression with robust variance estimators was used to identify demographic disparities in sexual identity. Results were presented as proportion ratio (PR) with 95% confidence interval (CI). Results Overall, 29,607 (2010), 20,249 (2014), and 22,558 (2021) individuals reported sexual identity. Heterosexual identity decreased from 95.7% (95% CI 95.4-96.0%) in 2010 to 89.0% (88.5-89.4%) in 2021, while bisexual identity increased from 1.4% (1.2-1.6%) in 2010 to 2.0% (1.8-2.3%) in 2014, and further up to 2.7% (2.4-2.9%) in 2021. Homosexual identity increased slightly from 1.5% (1.4-1.7%) in 2010 to 1.8% (1.6-2.0%) in 2021. Multivariate analyses showed that female, older age, and lower education were inversely associated, while never-married status and living alone were positively associated, with homosexual identity. In contrast, female, younger age, lower income (100 SEK/year) ( < =2,500 vs > 4,500: 2010: PR 3.32 [95% CI 1.92-5.75]; 2014: 1.83 [1.28-2.60]; 2021: 1.51 [1.14-2.01]), and never-married status (never vs currently married: 2010: 2.03 [1.47-2.80]; 2014: 1.92 [1.39-2.65]; 2021: 1.50 [1.15-1.95]) were positively associated with bisexual identity. Conclusions Heterosexual identity decreased while homosexual/bisexual identities increased in Stockholm County during 2010-2021. Socioeconomic disparities persist in sexual minorities and vary by sexual identity. Key messages • Marked socioeconomic disparities persist in sexual minorities and vary by sexual identity in Stockholm County, although income and marital status disparities in bisexual group seem narrowing. • Future studies are warranted to investigate the social dynamics that continue to produce sexual minority disadvantages.