Purpose: The purpose of this study is to estimate the population size of men who have sex with men (MSM) in Kazakhstan and their HIV testing history. Methods: We conducted structured interviews with MSM in four geographically disparate cities-N=400 (n = 100/city)-to implement four population estimation methods and ascertain HIV testing history. Results: Approximately 3.2% of men-corresponding to similar to 154,000 individuals-in Kazakhstan aged 18-59 are MSM. The 49.9% of the sample who reported taking an HIV test far exceeds the <1% reported as MSM in surveillance data. Conclusion: HIV testing surveillance in Kazakhstan has underestimated the number of MSM. This underscores the need to redress social and structural barriers to HIV testing and disclosure of sexual behavior experienced by MSM in Kazakhstan. Recommendations include promoting cultural sensitivity among testing staff through quality assurance and regular training, and increasing protection and public awareness through antidiscrimination policy development.