Global targets aim to increase the number of people living with HIV (PLWH) who know their status. Using data from Mozambican facility-based HIV testing and counseling (HTC) and a population-based survey, we compared characteristics of PLWH diagnosed in HTC to the general population of PLWH to identify subgroups that are missing from the health system and may be undiagnosed. Male and female PLWH aged 50+ (PPR=0.47, p=0.0001) and with higher HIV knowledge (PPR=0.52, p=0.004) were underrepresented in HTC. A higher proportion of patients diagnosed in health facilities were aged 25–39 (PPR=1.23, p=0.02). Female PLWH with lower economic (PPR=0.70, p=0.04) and educational status (PPR=0.86, p=0.02), and male PLWH aged 18–24 (PPR=0.47, p=0.03) were underrepresented in HTC. Comparing HTC data to population based data can inform efforts to increase HIV diagnoses and to ensure that all PLWH know their status