OBJECTIVES: Inadequate or partial treatment of Tuberculosis (TB) is a known factor that would promote drug resistance, thus increasing the overall cost of TB management.  The study objectives are to identify the general characteristics of defaulting patients and to estimate the cost impact on health authorities as compared to non-defaulters. METHODS: A retrospective case-control study was carried out in public treatment centres in Selangor, Malaysia. Defaulter is defined as TB patient who has interrupted treatment for two consecutive months or more and did not complete their treatment. All subjects were selected from 2011 TB District Registry database.  Patients’ medical case notes and baseline characteristics were reviewed and analysed.  The direct costs of TB management were estimated from public health cost references. The study was performed from a government’s perspective.      RESULTS: 176 defaulters and 204 non-defaulters were studied.  Foreign-born patients showed a higher risk  (OR= 5.929; p <0.01) of defaulting treatment. Unemployed patients were also more likely to default treatment (OR=1.521 p>0.05). Defaulters were more likely to default treatment during intensive phase as compared to maintenance phase (68.1% vs. 31.9%; p<0.05). No other significant findings were observed between the two groups including age, ethnicity, severity of x-ray changes, type of TB and overall medical risk factors. Mean cost of the non-defaulter group is higher than the defaulter group due to a complete treatment (RM 1,259.62 vs. RM 575.58; p<0.05). No significant treatment cost difference was observed in foreign-born defaulters as compared to local Malaysians (mean: RM 576.43 vs. RM 573.78; p>0.05). CONCLUSIONS: Data from this study suggest TB treatment should be completed to avoid a potential huge waste of resources. More attentions are required for foreign-born defaulters due to overall consequence in public health and management cost. Additional costs would be required if susceptible TB strains of the defaulters turned into more virulent strains.