This article first provided information on otolith shapes, the variation of otolith weight by sex, fish size, season, and sampling site, and the linear relationship between otolith weight and fish size. A total of 815 Periophthalmus chrysospilos specimens from Duyen Hai, Tra Vinh; Tran De, Soc Trang; Dong Hai, Bac Lieu; and Dam Doi, Ca Mau in the Mekong Delta ranged from 4.20 to 12.50 cm total length and from 1.26 to 16.88 g weight were analysed. The analysis results revealed that Ps. chrysospilos had a square otolith, deeply notched at the anterior apex and flat at the posterior apex. The weight of the left otolith showed a statistical difference according to survey factors, including gender, fish size, season, and sampling site. The otolith weight had a proportional relationship with to the total length, body weight, and head length of mudskippers (r2 = 0.7~0.9), which meant that fish size could be predicted from the otolith weight and about 70-90% of the otolith weight of Ps. chrysospilos varied corresponded the growth of the fish.