Otolith dimension and mass of Butis koilomatodon sampled along estuaries in Mekong Delta from January 2020 to December 2020 were used to test the similarity of left and right otolith in a pair, as well as the otolith variation between male and female monthly in four sampling locations. The left otolith was not different in size and mass from the right one. The otolith length and weight of males were greater than females but not the width. The highest otolith dimensions were recorded in the dry season, but the otolith weight was similar in both dry and wet seasons. Besides, otolith biometric and weight were also similar in four sampling sites. The otolith mass had relatively to fish body weight, demonstrating that otolith weight could be considered an indicator to predict the fish length, body height, head length, and weight.