The Mozambique Population-based HIV Impact Assessment (PHIA), INSIDA 2021 was a household-based national survey conducted between April 2021 and February 2022 to measure the impact of the country’s national and provincial HIV response. INSIDA 2021 included adults, defined as those aged 15 years and older, offered HIV counseling and testing with return of results and collected information about uptake of HIV care and treatment services. Of 8,998 eligible households, 96.5% completed a household interview. Among 19,912 eligible adults (11,098 women and 8,814 men), 14,488 (8,255 women and 6,233 men) were interviewed and tested for HIV. When accounting for enumeration area and dwelling unit response, 96.3% and 88.0% respectively, the overall response rate for adults was 59.5%: 60.8% for women and 57.8% for men.