The Cathedral of the Immaculate Conception on the zócalo was begun in the 16th century, making it one of the older colonial churches in the region. The current facade is largely 18th-century Baroque, with a simpler interior than the great cathedrals of Puebla or Oaxaca but notable for its scale relative to the town's modest size.
The cathedral's construction reflected Tehuacan's importance as a regional centre during the colonial period — the city was a significant stop on the route between Mexico City and Oaxaca. The church is still active and holds regular masses. The interior houses several colonial-era paintings and a carved retablo. Entry is free and the cathedral is usually open during daytime hours.