Tuberculosis remains a major health problem in many tropical countries, including Kenya. Defaulting from treatment has been an obstacle to treatment management control. Inability to complete the prescribed regimen is quite common in self-administered treatment and an important cause for treatment failure, relapses, acquired drug resistance and on-going transmission of infection. The objective was to determine factors associated with default from TB treatment in Busia County. A Cross-sectional descriptive study was conducted on 249 patients; sequential enrolment was conducted of TB patients collecting drugs within Busia County. The data was then converted to Stata 13 for further analysis. Descriptive statistics was used in the form of frequencies, tables, charts and graphs. To assess the association, Chi-square tests (����), t-test (for numerical variables) was used. Association was further tested using regression models; I carried out a univariate analysis on all the indicator variables and checked for statistical significance at 95% confidence intervals. Out of 249 study participants, 17 % (42) were defaulters and 83 % (207) were non-defaulters and males were 61% (152) while females were 39% (98). The characteristics that were statistically significant were history of alcohol consumption (OR 3.20; 95% CI 1.50 to 6.84 and P value 0.003), history and quantity of cigarette smoking (OR 3.20; 95% CI 1.50 to 6.84 and P value 0.001), vomiting (OR 2.07; 95% CI 1.06 to 4.06 and P value 0.033) and nausea (OR 1.99; 95% CI 1.01 to 3.89 and P value 0.046) as side effects experienced during taking TB drugs and taking TB drugs before meals (OR 1.99; 95% CI 1.01 to 3.89 and P value 0.043). Adherence to TB treatment in Busia County is a behavioral issue involving patient factors; alcohol intake, health care poor attitude and cigarette smoking that were most cited reasons for default, side effects were also cited to be a reason for defaulting like vomiting and nausea. Measures on patient behavioral indicators and maintenance of an effective communication channel between health facilities and patients during the treatment more focus on healthcare motivation, training and track patients on their intensive phase of treatment is recommended