Background: Data on heterogeneity in cancer screening and diagnosis rates among lesbians/gays and bisexuals is lacking. Recent studies showed that lesbians/gays and bisexuals have decreased healthcare utilization compared to heterosexual counterparts and continue to experience discrimination in healthcare. Few studies have examined how sexual orientation impacts cancer screening and prevalence. We, therefore, investigated the association between sexual orientation and prevalent sex-specific cancer including prostate, breast, and cervical cancer. Methods: This was a cross-sectional survey-based US study, including men and women aged 18+ from the Health Information National Trends Survey (HINTS) database between 2017-2019. The primary endpoint was individual-reported prostate, breast, and cervical cancer screening and prevalence rates among heterosexual and LGB men and women. Multivariable logistic regression analyses assessed association of various covariates with undergoing screening and diagnosis of these cancers. Results: Overall, 4,441 and 6,333 heterosexual men and women, respectively, were compared to 225 and 213 lesbian/gay and bisexual men and women, respectively. Lesbians/gays and bisexuals were younger and less likely to be screened for prostate, breast, and cervical cancer than heterosexuals. A higher proportion of heterosexual women than lesbian and bisexual women were screened for cervical cancer with pap smears (95.36% vs. 90.48% and 86.11%, p = < 0.001) and breast cancer with mammograms (80.74% vs. 63.81% and 45.37%, p = < 0.001). Similarly, a higher proportion of heterosexual men than gay and bisexual men were screened for prostate cancer with PSA blood tests (41.27% vs. 30.53% and 27.58%, p = < 0.001). Conclusions: Lesbians/gays and bisexuals in the US may be less likely to undergo screening of sex-specific prevalent malignancies, including prostate, breast, and cervical cancer. Healthcare professionals should be encouraged to improve cancer screening among lesbians/gays and bisexuals.