[1] It elects one deputy to the lower house of Congress for each three-year legislative session by means of the first-past-the-post system.

Votes cast in the district also count towards the calculation of proportional representation ("plurinominal") deputies elected from the second region.

[2][3] Under the National Electoral Institute's 2022 districting plan, which is to be used for the 2024, 2027 and 2030 federal elections and which gave Coahuila an additional district,[4] the 3rd district comprises 13 municipalities in the central-eastern portion of the state: Abasolo, Allende, Candela, Castaños, Escobedo, Guerrero, Hidalgo, Juárez, Monclova, Progreso, Sabinas, San Juan de Sabinas and Villa Unión.

The district's head town (cabecera distrital), where results from individual polling stations are gathered together and tallied, is the city of Monclova.

[5][1] Between 2005 and 2017, the district was located in the central-eastern portion of the state and covered the municipalities of Abasolo, Arteaga, Candela, Castaños, Escobedo, General Cepeda, Juárez, Monclova, Progreso, Ramos Arizpe, Sabinas and Sacramento.