The BBC sci-fi drama will hit the milestone on November 23, 2013, but Eccleston was reluctant to discuss his potential involvement in a celebratory special in an interview with RedCarpetNewsTV.
"Would I like to be involved? If I told you that, I'd have to shoot you," said the actor, who played the Ninth Doctor for a single 13-part series in 2005.
He then added: "I've not even thought about it. It's so long ago for me that I haven't even thought about it."
Eccleston also praised current Who star Matt Smith, though admitted that he has not watched any of the 30-year-old's episodes.
"I've not seen him as the Doctor, but I've seen him on stage - he's an excellent actor," Eccleston said.
Smith previously expressed his hope that Eccleston would return to Doctor Who for a guest appearance, but showrunner Steven Moffat has refused to confirm if a multi-Doctor story will form part of the 50th anniversary celebrations.
Earlier this year, Eccleston addressed his departure from Doctor Who and insisted that his "conscience is completely clear".
"I know what went on and the people who were involved know what went on - that's good enough for me," he explained.
Doctor Who returns to BBC One this Christmas with festive special 'The Snowmen'.
> Doctor Who's Best and Worst Multi-Doctor Stories: Friday Fiver
Watch Christopher Eccleston discuss Doctor Who's 50th anniversary below: