"The person was tested following their return to New Zealand as a precaution after showing minor symptoms. Following strict Ministry of Health advice, they immediately quarantined themselves from the public and their bubble," the club said in a statement.
"The staff member has praised both the club and the media for respecting his privacy and that of that of his family during a difficult time. He is now focusing on preparing for a potential finish of the Hyundai A-League 2019/20 season and beyond.
"No other staff member on the trip has tested positive for Covid-19."
The Phoenix made the trip over to Australia late last month with the idea of playing out the remainder of the A-League season across the Tasman due to travel restrictions introduced at the time by the New Zealand and Australian governments.
However, the season was suspended soon after the club arrived in Sydney, which saw them return to New Zealand.
When the season was suspended, the Phoenix still had nine games on their schedule and were well in the hunt for a spot in the playoffs with 11 wins from 20 games seeing them in third place on the ladder.
Football Federation Australia is set to make an assessment on the future of the rest of this season's competition on April 22, just under a month after the league went on hiatus.
