Tuberculosis is an infectious disease caused by Mycobacterium tuberculosis and is one of the world's top 10 main causes of mortality. Pulmonary tuberculosis is caused by germs (Mycobacterium tuberculosis) that typically target the lungs and is preventable and curable. There were 3,259 instances of pulmonary tuberculosis in Deli Serdang in 2018, 7,836 cases in 2019, and 7,840 cases in 2020, with an incidence rate of 92.06 percent per 100,000 people and an annual mortality rate of 90. The implementation of prevention of pulmonary tuberculosis transmission in the family has not been properly carried out, and that in Deli Serdang Regency there has never been research on preventing transmission of pulmonary tuberculosis disease in families; therefore, the authors are interested in conducting research on prevention of tuberculosis transmission based on families in Deli Serdang Regency, North Sumatra. The objective of this phenomenological study is to characterize in detail and with precision the significance of the experience of the closest family members living at home with tuberculosis patients in preventing transmission of pulmonary tuberculosis within the family. In-depth interviews performed to acquire information regarding informants' knowledge and experience with pulmonary tuberculosis and family measures to prevent TB transmission. Observations were conducted to get a knowledge of issue solving, including environmental variables, facial expressions, and observed behavior. Using the Nvivo 12 software, data processing was performed. The approach of phenomenological analysis for Interpretative Phenomenological Analysis (IPA) was used to analyze the data. The research yielded a series of themes that provide insight into family-based pulmonary tuberculosis transmission prevention in families with pulmonary tuberculosis. These themes also serve as markers of family-based tuberculosis transmission prevention in the Deli Serdang Regency. The results of the study demonstrate the necessity of family engagement in preventing the transmission of pulmonary tuberculosis for patients with pulmonary tuberculosis. The researchers' model for the prevention of pulmonary tuberculosis transmission incorporates numerous pre-existing ideas to identify and explain the factors that influence the prevention of pulmonary tuberculosis transmission in families. Some research limitations: 1. Pulmonary TB cadres have not been maximally empowered in the Gunung Meriah area, so that health workers are more optimal in monitoring pulmonary TB treatment e345 Family-