Introduction: Ethiopia is one of the countriesâ€™ most severely hit by HIV pandemic. Two percent ofrnnew HIV infection 3% of HIV-related death occurred in Ethiopia in 2017. The national adult HIVrnprevalence rate was 0.9% [1.2% in females and 0.7% males]. Index testing is focus on offering HIVrntesting to everyone exposed to HIV by the index case. Ethiopian Country Operation Plan (COP19) isrnfocused on active case finding using Index Case Testing (ICT) (minimum 20% yields) as a majorrncomponent of service delivery efforts. This research analyzed the HIV sero-prevalence among sexualrnpartners and children of Index cases. rnObjectives: To assess the magnitude and associated factors of HIV index testing among index casesrnon ART follow-up in selected government health facilities in lideta subcity, Addis Ababa, Ethiopia rnMethods: Mixed method facility-based cross-sectional study design was used. Pretested checklistrnwas used to retrieve information from the client's medical record and analyzed using SPSS version 23.rnResults were displayed in Odds ratio, confidence intervals, and P-value. Bivariate and multi variablernanalysis used to analyze HIV index testing and the factors associated with it. Qualitative data wasrncollected through in-depth interviews and analyzed using open code and thematic analysis approach. rnResult: A total of 385 index cases on patient card reviewed from ART follow-up. Out of two hundredrnninety-one partners 84% and from 481 children 91% were tested. Sixty percent of partners and 9.6%rnof children's test results were positive. The odds of HIV index testing were higher in male partnersrnAOR 8.43(1.32-8.94) than females. Index cases who had one children AOR of 7.59(2.39,26.95) andrntwo children AOR of 3.47(1.2,10.4) times more likely HIV tested than index cases with no children.rnThe qualitative test result showed that the major reasons for not testing their families were fearrndisclosure, fear of positive test result, stigma and discrimination and service related factors. rnConclusions and Recommendation: This study showed that high proportions of index partners andrnchildren have been tested for HIV. Out of tested partners, the majority test result was positive. Factorrnthat had a strong association with HIV index testing was being male partner and having one or twornchildren. The health institutions should strengthen ICT service in the ART unit to ensure thernsustainability of testing.