This study was conducted to determine the role of flower-visiting bats as pollinators at the mangrove areas of Peninsular Malaysia. The mangrove trees of the genus Sonneratia, even though reported mainly pollinated by bats, are lacking in research regarding their pollination ecology. Therefore, the effectiveness of bats as pollinators was studied from the pollen loads on their bodies, as well as from pollen grains deposited on the stigmata during their visits to the Sonneratia flowers (Sonneratia 'caseoiaris, S. alba and S. ovata). Observations of other nocturnal visitors of the flowers were conducted to further assess the relative importance of bats as pollinators. The flowering biology of the three Sonneratia species was also examined to infer the breeding system and reproductive synchrony of the trees and their pollinators. Bats were the effective pollinators of S. caseolaris and S. alba trees, depositing sufficient pollen grains on the stigmata for pollination. The flowering biology of these two Sonneratia species (flower morphometrics, nectar secretion rate, nectar sugar concentration and anthesis phase) also suggests that these species uses bats as their principal pollinators. Even though the morphology of the S. alba flowers and visitor observations indicated pollination by moths such as sphingids, bats nonetheless were responsible for depositing most of the pollen loads on the stigmata of the flowers. Examinations of reproductive parts (pollen and ovules) indicated that the three species show obligate autogamy. Exclusion experiments on S. caseolaris however showed reduced pollination success when bats were deterred from visiting the flowers, further confirming the importance of bats as Sonneratia pollinating agents as compared to other visitors.