To evaluate chronic pulmonary aspergillosis (CPA) as an alternative diagnosis of smear-negative tuberculosis (TB) and treatment failure in TB patients in Nigeria.We conducted a cross-sectional multicentre survey in human immunodeficiency virus (HIV) positive and negative adult patients at the end of their TB treatment in clinics in Lagos and Ilorin states. All were assessed using clinical examination, chest X-ray (CXR) and aspergillus immunoglobulin G (IgG) serology, and some for sputum fungal culture. CPA was defined as a positive Aspergillus fumigatus IgG titre with compatible CXR or a positive sputum culture of Aspergillus with a visible fungal ball on CXR with symptoms of underlying lung disease.Of 208 patients recruited between June 2014 and May 2015, 153 (73.6%) were HIV-positive. The mean age was 39.8 years, 124 (59.6%) were female and 39 (18.8%) were unable to work. The median CD4 count was 169.5 cells/ml (range 4-593) in HIV-infected patients with positive Aspergillus IgG. Overall, 109 (52.4%) had documented TB, 140 (67.3%) had a productive cough and 50 had haemoptysis. CPA prevalence was 8.7%; 10 (6.5%) had HIV infection and 8 (14.5%) were HIV-negative (Fisher's exact P = 0.092).CPA is a neglected disease in Nigeria, and most cases match the World Health Organization diagnostic criteria for smear-negative TB.