Introduction Prevention of Mother To Child Transmission (PMTCT) of HIV is one of the key strategies towards HIV epidemic control. Despite considerable progress in PMTCT of HIV over the past decade in Zambia, the country is yet to reach global and national target for elimination of Mother To Child Transmission of HIV. Avoidance of unintended pregnancy among women living with HIV provides is one of the cost-effective interventions in a comprehensive PMTCT of HIV approach. This study therefore aimed at ascertaining trends in and predictors of unmet need for family planning among women living with HIV in Zambia Methods The study employed a repeated cross sectional (RCS) study design, using data from the three (3) most recent consecutive rounds of the Zambia Demographic and Health Survey (ZDHS) conducted in 2007, 2013/2014 and 2018. The study used data from a total of 34,204 women aged 15-49 years from the three survey points, 2007, 2013/14 and 2018, among whom 4,985 were HIV positive, with a final sample size constituting 2,675 married women living with HIV. We used descriptive statistics and logistic regression analyses to respectively ascertain trends in and predictors of unmet need for family planning among married women living with HIV. Results Over the three survey points, unmet need for family planning among married women living with HIV has hardly declined, registering 22% in both the 2007 and 2018. Residence, age of women, household wealth, woman’s parity, employment, and age of spouse emerged as significant predictors of unmet need for family planning among women living with HIV in Zambia Conclusion Preventing one HIV infection in a child is averting lifetime costs of HIV treatment and associated healthcare costs. There is need to consider optimization of PMTCT interventions including shaping programming regarding prong 2 in a way that it responds to main causes of mother to child transmission of HIV in Zambia. Among other aspects, policy and practice needs to strengthen SRH/HIV integration and better target rural residents, younger women, those with high parity and consider positive male engagement to reduce unmet need for family planning among women living with HIV.