Species from the Mallomonas bronchartiana complex were examined using material from Vietnam, the U.S.A. and South Korea. The original description of Mallomonas bronchartiana is expanded and descriptions of two new taxa, M. pseudobronchartiana and M. velari, are given. All taxa possess body scales that are large, broad, with an asymmetrically-placed posterior rim, an internal honeycomb reticulation, and are covered externally with a layer containing papillae. A distinct V-rib is lacking on Mallomonas bronchartiana scales. Scales of M. pseudobronchartiana have a thin V-shaped rib situated on the scale surface, while the V-rib of M. velari is formed from an upward folding of the surface of the scale. Scales of Mallomonas velari are also easily separated from the other species by the presence of a large forward projecting wing. The positions of all three taxa within the genus are discussed, and placement in section Quadratae is proposed. The distributions and habitat conditions of each species are summarized.