Purpose: The aim of this study was to assess the orthodontic treatment complexity and need in Nigerian adolescents as well as to ascertain the relationship between these professionally assessed facets of orthodontic provision and the oral health-related quality of life in the adolescents. Materials and Methods: The orthodontic treatment complexity and need in 274 adolescents who were drawn from four secondary schools in Ibadan, Nigeria aged 12 to 17 years (142 (51.8%) females and 132 (48.2%) males) were examined using the index of complexity, outcome and need. The oral health-related impacts of the same subjects were assessed using the shortened version of the oral health impacts profile. In addition to the descriptive statistics, the Pearson chi-square test was used in the analysis of data. Results: Cases that were considered to belong to the easy complexity grade accounted for 20.1% while difficult/very difficult complexity grades accounted for 9.8%. Boys had significantly fewer complexity grades that were in the easy grade (P 0.05). Of the subjects, 42% would need orthodontic treatment and 62.4% had some oral health-related impacts, with boys suffering significantly more impacts than girls. The relationship between oral health-related impacts and treatment need was significant (P 0.05) unlike with complexity (P > 0.05). Conclusions: The orthodontic treatment complexity and need in these Nigerian adolescents was comparable to Caucasians including the association with oral health-related impacts on daily activities. Keywords: Nigerian adolescents, oral health-related quality of life, orthodontic treatment complexity and need