Background: HIV status disclosure facilitates receipt of HIV prevention and treatment services. Although disclosure to sexual partners, family members or friends has been extensively studied, disclosure to community-based HIV programs is missing. This study assesses the magnitude of, and factors associated with undisclosed HIV status to a community-based HIV prevention program among caregivers of orphans and vulnerable children (OVC) in Tanzania. Methods: Data are from the USAID-funded Kizazi Kipya project that seeks to increase uptake of HIV, health, and social services by OVC and their caregivers in Tanzania. Data on OVC caregivers who were enrolled in the project during January-March 2017 in 18 regions of Tanzania were analyzed. Caregivers included were those who had complete information on their HIV status disclosure, household socioeconomic status, and sociodemographic characteristics. HIV status was self-reported, with undisclosed status representing all those who knew their HIV status but did not disclose it. Multilevel mixed-effects logistic regression, with caregivers' HIV status disclosure being the outcome variable was conducted. Results: The analysis was based on 59,683 OVC caregivers (mean age = 50.4 years), 71.2% of whom were female. Of these, 37.2% did not disclose their HIV status to the USAID Kizazi Kipya program at the time of enrollment. Multivariate analysis showed that the likelihood of HIV status non-disclosure was significantly higher among: male caregivers (odds ratio (OR) = 1.22, 95% confidence interval (CI) 1.16-1.28); unmarried (OR = 1.12, 95% CI 1.03-1.23); widowed (OR = 1.12, 95% CI 1.07-1.18); those without health insurance (OR = 1.36, 95% CI 1.28-1.45); age 61 + years (OR = 1.72, 95% CI 1.59-1.88); those with physical or mental disability (OR = 1.14, 95% CI 1.04-1.25); and rural residents (OR = 1.58, 95% CI 1.34-1.86). HIV status non-disclosure was less likely with higher education (p < 0.001); and with better economic status (p < 0.001). Conclusion: While improved education, economic strengthening support and expanding health insurance coverage appear to improve HIV status disclosure, greater attention may be required for men, unmarried, widowed, rural residents, and the elderly populations for their higher likelihood to conceal HIV status. This is a clear missed opportunity for timely care and treatment services for those that may be HIV positive. Further support is needed to support disclosure in this population.