Forest decline has long been attributed to air pollution and acid rain/fog, with ozone having a record for damaging trees. This study investigated eco-physiological changes on Japanese red pine caused by simultaneous fumigation of O₃ (O) and fluoranthene (F) over a 90 day period. Seedlings were exposed individually or in combinations to 10 μM fluoranthene and O₃ (3 ppm and 6 ppm in 60 days and 90 days, respectively) inside growth chambers. Eco-physiological parameters monitored included gas exchange, chlorophyll fluorescence, needle chlorophyll content, and visual appearance. After 90 days, O + F treatment showed deleterious effects on visual needle appearance and the net photosynthesis rate near saturated irradiance. In addition, decreased levels in stomatal conductance, photochemical efficiency of PS II in the dark, and total chlorophyll and Chl a: Chl b were observed. F only treatment showed similar results but in lesser magnitude compared with F + O treatment. O treatment alone showed no significant negative effect, probably due to its low concentration in the 60 day treatment. The addition of mannitol (OH radical scavenger) mitigated O + F and F negative effects. Fluoranthene deposited on Japanese red pine presents great eco-physiological damage risk, even at low O₃ concentration. Furthermore, the effects of O₃ assisted phyto-toxicity of fluoranthene on red pine may have relevance to other plant species.