The 39-year-old is a free agent after leaving Australian side Sydney FC at the end of last season.
Former Celtic boss Neil Lennon tried to sign Del Piero for the Scottish Premiership side in 2012, but he opted to join Sydney instead.
"Two years ago it was interesting and it would be interesting again," Del Piero is quoted as saying by the Scottish Sun. "If we could talk then great. If you want I'll give you my phone number and you can pass it on!
"Celtic are a great team and I have always enjoyed playing in Scotland, so who knows? I know the league has changed with Rangers not being there, but they will be back soon enough.
"Celtic are also a club that could be in the group stage of the Champions League which is good. Sometimes to get there you just need a little bit of luck. Or experience."
Del Piero scored seven goals in 19 appearances for Sydney last season.