According to their trophic-niche breadth, bees can be classified as polylectic if they collect pollen from a wide variety of plant species or oligolectic if they obtain pollen from only a few species which usually belong to the same genus or even family. In this study, we measured the trophic-niche of Megachile maculata as well as its breadth in southeastern Brazil. Samples of pollen from nests were used to identify the plants visited by this bee. We found 11 different pollen grain types. Asteraceae occurred at high frequency (97.36%); 84.09% belonged to Baccharis and 12.31% to the genus Vernonia. Trophic-niche breadth of M. maculata varied little over the study period. The highest trophic-niche breadth was found at the end of the dry season and the lowest in November, at the beginning of the rainy season. We concluded that M. maculata is an oligolectic species and Baccharis and Vernonia are important pollen sources.