[Objectives]  To investigate the nest structure, distribution of castes, and the total number of individuals, in nests of Ancistrotermes dimorphus Tsai et Chen. [Methods]  Nests were located and dissected to reveal their structure. Statistical methods were used to determine the distribution of castes within nests and the total number of individuals in each nest. [Results]  Nests of A. dimorphus consist of a fungus garden, a termitarium galley, a queen’s chamber, a swarming exit room and a swarming exit hole. The total number of individual termites (including eggs) in each nest ranged from 12 255-24 230. Eggs, larvae, nymphs, workers, soldiers and winged adults were scattered throughout the nest chamber rather than segregated in particular areas. [Conclusion]  Nests of A. dimorphus are of the extreme dispersed type and contain fewer individuals than those of other termite species.