This paper assessed biochemical parameters in leaves of selected ornamental species growing in urban areas of southwest Nigeria to obtain the air pollution tolerance index (APTI) and anticipated performance index (API) for classification into tolerant and sensitive species against air pollution. Four sites and three ornamental species (Polyalthia longifolia, Thuja occidentalis and Duranta repens) common to the sites were used for this study. Results showed significant variations in biochemical variables, hence biochemical parameters cannot be used solely to categorize the species. APTI values obtained suggested that P.  longifolia    is tolerant species to air pollutants while T. occidentalis and D. repens are sensitive species that can be used as bioindicators of air pollutants. The API value revealed P. longifolia and T. occidentalis to be poor performer and very poor performer respectively while D. repens cannot be recommended for greenbelt development. Therefore, T. occidentalis and D. repens, can be recommended as bioindicators of poor urban air quality.