Bactrocera dorsalis Hendel, (Diptera: Tephritidae) is one of the serious fruit pests in Sri Lanka. The present study aims to investigate the abundance of B. dorsalis adults and their infestation levels on Willard (Wld) and Karutha kolomban (Kc) mango varieties grown in main bio-climatic zones of Sri Lanka.The study was conducted from September 2020 to February 2021 in 08 study sites of 04 main bio-climatic zones. In every month, flies were collected from field traps. Infested fruits were also collected from study sites and fruit fly infestation levels and adult emergence were studied in the laboratory. The significance levels in the variations of percentage infestation, adult emergence and abundance of caught flies were compared among varieties, study sites, and with the climatic variables. Mean weight (g) of the tested mango fruits were (112.71 ± 1.78) g and (290.75 ± 4.23) g for Wld and Kc respectively. The intermediate zone recorded the highest percentage of average infestation (Wld, p>0.05; Kc, p<0.05) and the highest mean value for the adult emergence for both varieties. The adult emergence for Kc was higher than the Wld in all study sites and it was significantly varied between mango varieties (p<0.05). The highest number of B. dorsalis were collected from traps in the intermediate zone (Wld, p<0.05; Kc, p>0.05). The infestation percentages, adults emergence and the abundance of caught flies increased significantly with the time of the study for Wld and Kc (p<0.05). The abundance of trapped flies was significantly varied between mango varieties (p<0.05) and positively correlated with the fruit infestation (p<0.05). Trap collections for Kc in the intermediate zone showed a significant positive correlation with the rain fall. The study results on the variation of abundance and damaging levels of B. dorsalis on two commercially important mango varieties grown in main bio-climatic zones of Sri Lanka will be helpful to design further studies and control measures.