Objective. The tyrosine kinase inhibitors have markedly changed the disease course for patients with Ph(+) and/or BCR-ABL1 (+) chronic myeloid leukemia (CML). This study was embarked upon to assess the long-term effects of imatinib therapy on survival in adult Nigerian patients with CML. Methods. All adult patients on imatinib (400-600 mg) seen from July 2003 to December 2010 were assessed. Male/female distribution was 171/101, with a median age of 38 (range, 20-75) years. Overall survival (OS) and progression-free survival (PFS) were determined using the Kaplan-Meier techniques. Results. Of all the 272 patients, 205 were in chronic phase, 54 in accelerated phase, and five in blastic phase, at commencement of imatinib. As at December 2010, 222 were alive. OS at 1 and 5 years was 94% and 63%, while PFS was 89% and 54%, respectively. Similarly, amongst the 205 patients in chronic phase, OS at 1 and 5 years was 97% and 68%, while PFS was 92% and 57%. Conclusion. Imatinib's place as first-line therapy in the treatment of CML has further been reinforced in our patients, with improved survival and reduced morbidity, comparable with outcomes in other populations.