Introduction: To achieve the elimination of mother to child transmission of the human immunodeficiency virus (HIV), preventing unintended pregnancy and reducing the high unmet need for family planning among HIV positive women was crucial. Despite being crucial little has been known on the unmet need for family planning and its determinants among women living with HIV in the rural area. Therefore, this study aimed to assess the prevalence of unmet need for modern family planning and its determinants among women Attending HIV Care Services at rural Public Health Facilities.Methods: An institution-based cross-sectional study was conducted from March to April 2020 in rural South Gondar. A total of 931 respondents were included in the study. To recruit respondents a multi-stage sampling technique was used. The data were collected using a pretested and semi-structured questionnaire. Data were entered by Epi data version 4.6 and exported to Stata version 14 for analysis. Variables with a p-value<0.2 in the bivariable logistic regression model were fitted to the multivariable logistic regression model. Adjusted Odds ratio with 95% CI was computed and variables with P-value < 0.05 in the multivariable analysis were taken as significant determinants.Results: The prevalence of unmet need for family planning was 25.67% with 95% CI (22.9628.58). Age group (3549) (AOR=6.5,95% CI (2.86,14.66)), education status (912) (AOR=0.25,95%CI (0.10,0.61)), history of ever use Contraception (AOR=3.9, 95%CI (2.28, 6.67)), having five and above parity (AOR=5.1, 95%CI (2.08, 12.43)) and not Counselling for contraception (AOR =4.2, 95 CI, (1.91, 9.37)) were determinant for unmet need of contraception among HIV positive women in South Gondar.Conclusion: prevalence of unmet need for family planning was high. It was mainlyInfluenced by last reproductive age group (35-49)), education (9-12), having no experience of contraception use, having five and above parity, and no counseling for contraception. Therefore, family planning programs need to focus on old (35-49) reproductive age women, and multi-para women.