Background Although tuberculosis (TB) care is provided free of charge in Morocco, a high number of patients voluntarily interrupt their treatment before the end. Treatment Default is a major obstacle in the fight against the disease. The purpose of this study was to describe the impact of knowledge and attitudes toward TB on treatment adherence. Methods Case-control study of 290 TB patients (85 defaulters and 205 controls). A defaulter was defined as a TB patient who interrupted treatment for two months or longer. Socio-demographic measurements, knowledge and attitude were collected by face to face anonymous questionnaire. Khi-square test was conducted to examine differences in TB attitudes and knowledge according to treatment adherence. Results The mean age of participants was 31.7 ± 12.0 years. Monthly income was under 2000 MAD (180 €) for 82% of them. Over sixty four percent were illiterate or had a basic educational level. Microbial cause was known by 17.2% respondents; 20.5% among adherent patients versus 9.4% (p=0.02). The fact that the disease is curable was more known by adherent patients: 99.0% versus 88.2% (p < 0.01). Eighty tree per cent of patients had been informed about treatment duration and consequences of not completing treatment: 89.0% among adherent patients versus 69.7% (p<0.001). The main reason evoked for defaulting was the sensation of being cured (72.9% of defaulters). Conclusion This study shows a poor knowledge on TB especially among non adherent patients. This finding justifies the need to incorporate patient's education into current TB case management.