BACKGROUND: In Myanmar, HIV is concentrated among key populations, yet less than half of the estimated 250,000 men who have sex with men (MSM) and transgender women (TW) report recent HIV testing. As many as 50% of MSM and TW may conceal their same-sex preferences and behaviors, yet little is known about the barriers faced by those who are locally regarded as 'hidden' - that is, MSM who do not disclose same-sex preferences and/or identify as gay. This study explored specific barriers to accessing HIV testing and other prevention services among 'hidden' MSM to inform appropriate models of service delivery. METHODS: In-depth interviews with MSM (n = 12) and TW (n = 13) and focus group discussions (FGD) with MSM and TW community members, leaders and key informants (n = 35) were undertaken in Yangon during June - September 2015. Participants were recruited by word-of-mouth by trained peer data collectors. Responses to questions from semi-structured guides were transcribed and coded using Atlas Ti. Codes were based on key domains in the guides and applied to transcripts to identify and analyze emerging themes. RESULTS: Fear of stigma and discrimination and the need to meet gender expectations were key reasons for non-disclosure of same-sex preferences and behaviors; this typically manifested as avoidance of other MSM and settings in which sexual identity might be implicated. These concerns influenced preference and interaction with HIV services, with many avoiding MSM-specific services or eschewing HIV testing services entirely. The difficulties of engaging hidden MSM in HIV prevention was strongly corroborated by service providers. CONCLUSION: Hidden MSM face multiple barriers to HIV testing and prevention. Strategies cognizant of concerns for anonymity and privacy, such as One-Stop Shop services and online-based health promotion, can discretely provide services appropriate for hidden MSM. Enhanced capacity of peer-service providers and mainstream health staff to identify and respond to the psychosocial challenges reported by hidden MSM in this study may further encourage service engagement. Overarching strategies to strengthen the enabling environment, such as legal reform and LGBTI community mobilisation, can lessen stigma and discrimination and increase hidden MSM's comfort and willingness to discuss same-sex behavior and access appropriate services.