Medication noncompliance hinders effective tuberculosis control. This descriptive study investigates the factors contributing to medication noncompliance among new patients with smear-positive pulmonary tuberculosis on treatment at government health institutions in Colombo, Sri Lanka. In a cohort of patients aged ≥15 years (n = 326), 23% were found to be noncompliers (n = 74) on follow-up. The median age of noncompliers (50 years) was significantly higher than the compliers (45 years). In multivariate logistic regression analysis, factors associated with noncompliance are as follows: being a male, living alone or with extended family, experiencing side effects to medication, perceiving nonsusceptibility to adverse effects of illness, and perceiving no benefit in regular treatment. The participants of a focus group discussion on service factors opined that the reception at treatment facilities and the interaction with certain categories of staff were poor. Noncompliance is related to a multiplicity of factors involving patients and healthcare services.