Modesto Main Jail is located at 1115 H. Street, Modesto, CA 95354. The mailing address is P.O. Box 649, Modesto, CA 95353-0649. The Modesto Main Jail is a direct supervision facility that houses approximately 1,000 inmates. The average daily population is about 950 inmates.

The Modesto Main Jail consists of five modules which include the following: booking, medical, administrative segregation, special housing, and general population. The booking area is where inmates are first processed and housed until they are arraigned in court. The medical module provides health care services to inmates. The administrative segregation module houses inmates who have been segregated from the general population for disciplinary or security reasons. The special housing module includes cells that are used for inmate isolation, protective custody, and suicide watch. The general population module is where the majority of inmates are housed.

The Modesto Main Jail offers a variety of programs and services to inmates including educational programs, religious services, substance abuse treatment, and mental health services. Inmates also have access to recreation, library services, and medical care.