In this work we document a case of mass swarming of the Mexican soldier beetle Chauliognathus vestitus Champion, 1914 from El Terrero locality, within the Sierra de Manantlan Biosphere Reserve, in Colima, Mexico. Two other species of soldier beetles Chauliognathus togatus Waterhouse, 1878 and Chauliognathus sp. were observed at El Terrero, coexisting with C. vestitus, but their numbers were considerably lower. An updated list of Chauliognathus species from the state of Colima is included. Our observations are the record, to our knowledge, of the second cantharid species exhibiting a mass flying behavior among more than 450 described Chauliognathus in the world, and the first record of this behavior among soldier beetles in the American continent.