The West Australian reports the ex-A-League frontman told Fremantle Magistrates Court he will plead not guilty to the offences, which include 10 counts of aggravated possession of a firearm, possession of methamphetamine and cannabis and three counts of possession of stolen property.
Mrdja has also been charged by Western Australian Police with two counts of possession of a silencer, possession of drug paraphernalia, being an unlicensed person in possession of a firearm or ammunition, cultivating a prohibited plant and receiving.
The 40-year-old was a former star for Perth Glory in the NSL, scoring 25 goals in 74 appearances for the club between 2000 and 2004 - including their 2004 NSL grand final win against Parramatta.
Mrdja was one of Central Coast Mariners first signings ahead of the inaugural A-League season but a serious knee injury plagued his six-year stay at the Gosford-based club, limiting him to only 48 games between 2005 and 2011.
An Australia call-up came for Mrdja in 2007, coming on as a 62nd-minute substitute during the Socceroos' friendly clash against Argentina.
It would be Mrdja's only appearance for the national team.
The striker announced his retirement in 2011 after a brief loan stint at Melbourne Victory, calling an end to a 13-year career.
Mrdja was released on bail and will appear at Perth's Magistrate's Court when his case resumes on June 5.
