She was quickly surrounded by supportive Democrat colleagues.
Votes in favour the bill poured in after her ballot was cast, after initally slow progress, reports said.
Democrat minority leader Nancy Pelosi tributed Ms Giffords' return.
"There isn't a name that stirs more love, more admiration, more respect, more wishing for our daughters to be like her than the name of Congresswoman Gabby Giffords. Thank you, Gabby," she said.
A post on Ms Giffords Facebook wall today said voting for the bipartisan bill was an important step in her recovery.
Mr Obama yesterday said the deal was a compromise necessary in an intensely partisan US political environment.
"Is this the deal I would have preferred? No.
"I believe we could have made the tough choices required.. right now.
"This compromise does make a serious downpayment on the deficit reduction we need. It will allow us to avoid default... and end the crisis that Washington imposed on the rest of America."
Obama credited the voice of the American people with turning the tide in the debt debate that has gripped Washington for weeks.
He said the debate had done damage to the US economy.
"This process has been messy. It has taken far too long. I am concerned about the impact it has had on business confidence and consumer confidence."
The compromise deal still is set to go before the Democrat-controlled US Senate tomorrow. It is expected to pass.
- HERALD ONLINE