East Mountain is a city in Upshur and Gregg counties, Texas, United States. The population was 899 at the 2020 census, an increase over the figure of 797 tabulated in 2010. East Mountain is located in southeastern Upshur County. Small portions of the city extend south along Gilmer Road and Coulter Road into Gregg County. The city limits extend northwest along Main Street and Medlin Road as far as East Mountain, a 660-foot wooded summit overlooking the community.