The Torchwood actor has been vocal about his desire to return to Doctor Who, despite the fact that he is currently playing Malcolm Merlyn on US series Arrow.
Barrowman has now suggested that he is still hoping to receive a call from Doctor Who showrunner Steven Moffat, according to The Los Angeles Times.
"I haven't been asked. I would love to [come back to Doctor Who] if they ask me," he stressed.
He went on to say: "[Arrow producer] Andrew Kreisberg has already said if they want me in the 50th anniversary, he will give me the time off to do it. But it's not up to me."
Barrowman's character Captain Jack Harkness debuted in the series one two-part story 'The Empty Child'/'The Doctor Dances', which was written by Moffat.
Captain Jack subsequently teamed up with The Doctor again in three episodes in the third series, and in the series four finale 'The Stolen Earth'/'Journey's End', where Torchwood, Sarah Jane Smith, Rose Tyler, Martha Jones and Donna Noble foiled a universe-ending plot by Davros and the Daleks.
Barrowman's spinoff show Torchwood aired its fourth series in 2011.
New Doctor Who companion Jenna-Louise Coleman recently promised that the 50th anniversary will be an event fans will remember for the rest of their lives.
The series returns with new episodes later this year on BBC One in the UK and BBC America in the US.
Watch Matt Smith and Jenna-Louise Coleman speak to Digital Spy about Doctor Who below: