The father of retired Australian tennis player Mark Philippoussis has been arrested in a morning raid on suspicion he molested two children.

Nikolaos Philippoussis, 68, is facing 14 counts of child molestation on two minors he was coaching, the San Diego County Sheriff's Department said in a statement.

Sheriffs Department documents allege one of the minors is under 10 years old.

The 68-year-old was arrested at his home in Mira Mesa on Tuesday (local time), a neighbourhood in San Diego, California.

"He didn't know we were coming," Lieutenant Greg Rylaarsdam said of the arrest.

Nick Philippoussis watches son Mark Philippoussis play against Dominik Hrbaty of the Slovak Republic in a men's singles match in the Hopman Cup at the Burswood Dome in Perth on January 2005. (AFP)

A search warrant was executed on the property, but authorities declined to say if computers or other property were seized.

Mr Philippoussis worked as a personal tennis coach in neighbourhoods north of San Diego, and detectives haven't ruled out the possibility of more alleged victims.

“In this particular case we are in the infancy of the investigation," Lt Rylaarsdam said.

"On a lots of cases we go all the way to the end and get all of our facts in order and all of the evidence lined up and then we go out and arrest somebody.

"But in a case like this where there is the potential of ongoing victimisation we developed probable cause and went out and arrested him when we had that.”

Mr Philippoussis is now being held in San Diego Central Jail on A$3.17 million bail.

The bail amount could be reduced when he is scheduled to make his first appearance at a San Diego courthouse tomorrow (AEST)

Nikolaos "Nick" Philippoussis. (9NEWS)

Known as "Nick", Mr Philippoussis served as coach and mentor to his son during his professional playing career.

Mark was just six when he took up the racquet at his father's urging, and was once ranked number eight in the world.

In a Father's Day tribute on Instagram last September, Mark told his father: "Thank you for your support, guidance and always being there for me no matter what no questions asked. Love you".

"Love you to (sic) Son, Thanks," his father replied.