Two of the alleged victims were lone females, walking to school in a pedestrian walkway near the 101 Freeway at Belmont Street.
The third incident involved a 12-year-old girl who was walking with her mother near the 101 overpass on Bonnie Brae Street.
Officers believe the suspect loiters frequently in the area between Belmont and Bellevue streets, called "the View" because it overlooks Echo Park.
The suspect is described as a Hispanic man with a dark complexion, between 18 and 30 years old, about 5 feet, 4 inches tall and 150 pounds.
He has short black hair, a mustache and acne.
Anyone with any information is asked to call LAPD's Rampart division detectives at (213) 484-3624.