[10] Johnson City is located in central Blanco County about 1 mile (2 km) south of the Pedernales River.

According to the United States Census Bureau, Johnson City has a total area of 1.8 square miles (4.7 km2), all land.

[2] Johnson City experiences a humid subtropical climate, with hot summers and a generally comfortable winter.

As of the 2020 United States census, there were 1,627 people, 725 households, and 415 families residing in the city.

24.0% of all households were made up of individuals, and 12.7% had someone living alone who was 65 years of age or older.

[16] Pedernales Falls State Park is located 10 miles (16 km) east of Johnson City.

Selah, Bamberger Ranch Preserve is a nearby wildlife sanctuary with a man-made batcave.