Ronnie Gamez, 27, was arrested in Laguna Niguel. Gamez coached girls soccer teams in the 11-, 13- and 17-year-old age groups.
Parents of an alleged victim found inappropriate communications between Gamez and the child. Sheriff's officials said an inappropriate sexual relationship allegedly began in February 2014 and lasted through March.
The Orange County Sheriff's department is seeking help identifying other possible victims.
Anyone with information regarding possible additional victims or any information they believe may assist in this investigation is asked to contact the Orange County Sheriff's Department Special Victims Detail at (714) 647-7419, or submit an anonymous tip to OC Crime Stoppers at (855) TIP-OCCS or at occrimestoppers.org.