In this research, a total of 186 metacarpal and 275 metatarsal bones were used from the 4739 bovine bones which were collected from the Yenikapi Metro and Marmaray excavation of the port of Theodosius in Istanbul. The bovine bones were investigated by radiocarbon (14C) dating, and the cattle bones between Early Byzantine (4th-7th centuries) to Late Byzantine (15th century). A total of 16 osteometric measurements were taken from each metapodial. When the withers height was estimated according to the Matolcsi multipliers without regard to the gender differences of the metapodial bones, it was observed that they varied between 120.97 and 123.52 cm on average. The presence of individuals with withers heights ranging from 103.45 to 148.10 cm suggests the existence of improved cattle breeding to obtain larger animals as well as steer cattle. The wide interval scale of the withers heights seen in the Byzantine cattle suggests that Roman animal breeding was still an influence in this period. However, the presence of small-size cattle in the port area of Theodosius also suggests the presence of smaller, local individuals.