Individuals with diverse sexual orientations face discrimination, stigma, victimization, concealment, etc., which tend to have a negative impact on their psychological and social functioning. Research indicates that self-acceptance is the psychological armor that has a major impact in alleviating social-emotional issues and promoting life satisfaction and well-being. Thus, the present study is an attempt to assess self-acceptance, self-acceptance of sexuality and mental health among lesbian, gay, and bisexual (LGB), and heterosexual young adults. It was hypothesized that individuals identifying as LGB would have lower general self-acceptance, lower self-acceptance of sexuality, and poorer mental health compared to heterosexual individuals. The sample of LGB adults (L (N = 45) G (N = 45) and B (N = 46)) and heterosexual adults (men = 45 and women = 47) with total N = 228 in the age range of 18–35 years (M = 25.12, SD = 4.86) were assessed using Berger’s Self-Acceptance Scale (Berger in J Abnorm Soc Psychol 47:778–782, 1952), the Self-Acceptance of Sexuality Inventory (Camp et al. in Psychol Sex Orient Gender Divers 9:92–109, 2022) and Keyes’ Mental Health Continuum (Keyes in J Consult Clin Psychol 73:539–548, 2005). The obtained data were subjected to One Way Analysis of Variance (ANOVA). The findings revealed significant differences on Self-acceptance (SA) (F = 89.84; p < 0.01), Self-acceptance of Sexuality (SAS) (F = 17.64; p < 0.01), and Mental Health (MH) (F = 51.53; p < 0.01). It is revealed that LGB adults had lower general self-acceptance, lower self-acceptance of sexuality, and poorer mental health in comparison to heterosexual adults. Significant implications can be observed from the results for mental health practitioners, healthcare practitioners, and the general public alike.