The neighborhood is bounded by Brown's Canyon/Chatsworth on the south and west, Northridge on the south, and Granada Hills on the northeast and east. The Santa Susana Mountains, which separate the San Fernando and Santa Clarita valleys, lie to the north. The principal thoroughfares are Mason Ave., Corbin Ave., Porter Ranch Drive, Tampa Ave. and Reseda Blvd., running north-south, and Sesnon Blvd., Rinaldi St. and the Ronald Reagan Freeway (State Route 118), running east and west. The Porter Ranch ZIP code is 91326.
Porter Ranch is in the hilly northwestern tip of the San Fernando Valley, where, according to a 2008 Los Angeles Times article, it was a "calm outpost of Los Angeles" that attracted residents "seeking sanctuary from the urban hubbub." It was noted that the neighborhood had "some of the cleanest air in the Valley year-around—some of which is attributable to winds that sweep through the community regularly." Nevertheless, "those same winds, which have been clocked at 70 mph, take down trees and holiday lights."