Mosley was due to face Mundine at the Sydney Entertainment Centre on Wednesday in a bid to prove his title credentials at light-middleweight once again.
The 42-year-old refused to attend Monday's press conference after reportedly still being owed over £400,000 for the bout by the event's co-promoter Millennium Events.
'Sugar' Shane released a short statement announcing that he will return to the USA over an alleged breach of contract from Millenium Events after checking out of his Sydney hotel last night.
A short Molsey statement read: "I'm very disappointed with this turn of events because I was planning on making a big statement by beating Mundine, but I was left with no choice but to withdraw.
"The fans in Australia have welcomed me with open arms, and I hope to return to fight for them one day in better circumstances."
Mosley's stellar 20-year professional career includes a pair of victories over Oscar De La Hoya, but 'Sugar' has won just once since 2010.