Sexual health education experienced by lesbian, gay, and bisexual (LGB) youth varies widely in relevancy and representation. However, associations among sexual orientation, type of sex education, and exposure to affirming or disaffirming content have yet to be examined. Understanding these patterns can help to address gaps in LGB-sensitive sex education. Our goal in this study was to examine the prevalence and associations among abstinence-only until marriage (AOUM) and comprehensive sex education with LGB-affirming and -disaffirming content sought/received before age 18 (from 1999 to 2014) by sexual orientation (completely heterosexual with same-sex contact, completely heterosexual with no same-sex contact, mostly heterosexual, bisexual, gay/lesbian) in a sample of 12,876 US young adults from the Growing Up Today Study. Compared to completely heterosexual referents, LGB participants who received AOUM sex education were more likely to encounter LGB-disaffirming content, and this effect was largest among sexual minority participants. Conversely, exposure to comprehensive sex education was associated with receipt of LGB-affirming information. Overall, participants commonly reported receiving AOUM sex education, which may lead to deficits and potential harm to sexual minorities.