She tweeted a video of her appearance and wrote: “Not even that long ago, this felt so far off.
“Delighted to return to (virtual) Parliament representing the people of East Dunbartonshire.
“My heartfelt thanks to colleagues and well wishers across the country.”
Speaker Sir Lindsay Hoyle said: “Can I say how pleased I am to see you Amy and welcome back, it really is good,” while Mr Williamson also welcomed her back and wished her the “very, very best”.
Before asking her question Ms Callaghan expressed “a heartfelt thank you to everyone who wished me well during my recent illness.”
The 28-year-old, who defeated former Liberal Democrat leader Jo Swinson for the seat in the 2019 general election, was found by her partner after falling ill at her home last June.
She left the Queen Elizabeth University Hospital in Glasgow in October after four months of treatment and rehabilitation.
At the time she tweeted a picture of herself in front of the facility holding a crutch aloft, and wrote: “To the miracle team at @NHSGGC PDRU – now my second family – thank you, I can never, ever repay you.
“I was wheeled in here. Now I’m walking out. I’m just getting started too.”