Pulmonary tuberculosis (TB) is an infectious disease that is a global health problem. Prevention of pulmonary TB transmission requires the active role of the family in providing support that contributes to preparedness to prevent transmission. Family support is considered important in building an environment that supports recovery and prevents the spread of TB. This study aims to identify the relationship between family support and preparedness in preventing pulmonary TB transmission in families of TB patients. Methods: This study used a quantitative design with a cross-sectional approach. A total of 100 family respondents of pulmonary TB patients in the working area of Puskesmas X were involved through purposive sampling method. Data were collected using a structured questionnaire and analyzed with the chi-square statistical test to see the relationship between variables. Results: The results showed that most families of patients with good family support had a higher level of preparedness in preventing pulmonary TB transmission (p < 0.05). Emotional support and information from the family were the dominant factors influencing preparedness. Conclusion: Family support plays a significant role in improving preparedness to prevent pulmonary TB transmission. Family-based interventions, such as education and counseling, can be an effective strategy to improve family preparedness in dealing with this disease.