Unsuccessful treatment of pulmonary tuberculosis results from medication non-adherence. Family is a significant source of support for adults with pulmonary tuberculosis but has limited ability to continuously support in the first six months of treatments. This randomized controlled trial, a two-arm post-test-only design was utilized to investigate the effects of the family empowerment program on medication adherence and treatment success among adults with pulmonary tuberculosis. The sample comprised 64 family members caring for newly diagnosed adults with pulmonary tuberculosis who visited a tuberculosis clinic of a university hospital in central Thailand. The participants were assigned randomly to either the experimental arm (n = 32) to receive the program or the control arm (n = 32) to receive only usual care. Data were collected using the Demographic and Pulmonary Tuberculosis-related Characteristic Data Collection Form, Family Member’s Demographic Characteristic Data Collection Form, Tuberculosis Medication Adherence Scale, and criteria to identify tuberculosis treatment success of the World Health Organization. Data were analyzed using descriptive statistics, Pearson’s chi-square, Fisher’s Exact, and McNemar tests. The results showed that the experimental arm had significantly higher medication adherence at the 3rd and 19th weeks after the program ended than the control arm. The experimental arm had a significantly higher treatment success rate at the 19th week thanthe control arm. The family empowerment program was effective in improving medication adherence and treatment success. Nurses need to be trained to empower family members in providing continuous support for adults with pulmonary tuberculosis. To fully assess the program’s effectiveness, additional research is required to investigate its performance in different contexts and with various samples.