Despite routine vaccine use, sporadic outbreaks of infectious coryza in poultry continue to occur in Taiwan. This study was designed to determine the serotypes and the complete nucleotide sequences of a hemagglutinin gene (HMTp210) of Avibacterium paragallinarum isolated in Taiwan between 1994 and 2017. Hemagglutination inhibition tests showed that these isolates belong to serogroups B and C. Sequence analyses of the HMTp210 gene showed that Taiwanese serogroup B isolates are most similar (94.7%–98.2% identity) to strain FARPER-174 isolated in Peru in 2015. In contrast, Taiwanese serogroup C isolates are most similar (96.3%–99.8% identity) to strain H-18 isolated in Japan in 1976. This is the first report showing the presence of A. paragallinarum of serogroup B in Taiwan. In addition, one Taiwanese isolate showed cross-reactivity with serogroup B and C antisera. This isolate contains a chimeric HMTp210 gene that might result from recombination between serogroups B and C. These findings could be valuable for the epidemiologic study and molecular serotyping of A. paragallinarum.