Tuberculosis (TB) is still a major public health problem in Nigeria and like other countries with the disease burden, the cure rate target of 85% set by World Health Organisation has not been achieved. Although interventions by pharmacists have been reported to improve drug therapy outcomes, the pharmacists are often not directly involved in the management of the patients in the country. The aim of this study is to determine the possible impact of pharmacist’s intervention on DOTS (Directly Observed Treatment Short Course) success rate in a DOTS centre in Nigeria. In this randomized controlled intervention study, 143 TB out-patients (age range = 8-56 yr; male = 78; female = 65) attending DOTS Centre in Olabisi Onabanjo Teaching Hospital in Sagamu, Nigeria were randomly allocated into intervention (71) and control (72) groups. Patients in the intervention group were educated on TB, counseled on their treatment and drug adherence, and monitored by a pharmacist for the duration of their TB treatment. Their treatment outcomes were statistically compared with those in the control group. The relationship between the treatment outcomes, and the age and sex was determined using both logistic regression and relative risk analyses. Available drug records in the hospital were evaluated and the pharmacists in the hospital as well as the nurses in DOTS Centre were interviewed to determine access to drugs. The results obtained showed that the active involvement of a pharmacist in a DOTS centre significantly improved the TB treatment success rate from 62.4% in the control group to 87.3% in the intervention group (p<0.001; relative risk, RR=1.397, 95% CI=1.144-1.706). Default from treatment significantly reduced from 26.4% in the control group to 8.5% in the intervention group (p=0.007; RR=0.320, 95% CI=0.136-0.755). The increase in treatment success rate and reduction in default from treatment were related to either age or sex. Proportions of those that died in the intervention and control groups were statistically similar and unrelated to either age or sex (p>0.05). In conclusion, a TB treatment success rate greater than the World Health Organisation minimum target of 85% success rate in TB management has been achieved in DOTS Centre following the involvement of a pharmacist in the care of the patients. Continuous education and counseling of TB patients are paramount to successful treatment outcomes in DOTS programmes. It is recommended therefore that pharmacists should always be part of the personnel in DOTS centers across the country.Keywords: DOTS programme; Randomized controlled study; Intervention study; Treatment outcomes; Southwestern Nigeria.