According to the United States Census Bureau, the city has a total area of 4.0 square miles (10.3 km2), of which 2.0 acres (8,234 m2), or 0.08%, are water.

[3] As of the 2020 United States census, there were 6,460 people, 1,537 households, and 1,400 families residing in the city.

10.3% of all households were made up of individuals, and 6.3% had someone living alone who was 65 years of age or older.

Peñitas is served by the La Joya Independent School District.

The United States Postal Service operates the Peñitas Post Office.