Police said Mr Brogden was found unconscious in a back room of his northern beaches electorate office at about 10.30pm on Tuesday.
The 36 year old was rushed by ambulance to Royal North Shore Hospital with what police said were self-inflicted injuries.
Mr Brogden’s wife, Lucy, remained at his side for most of the night.
The suicide attempt follows Mr Brogden’s resignation as Liberal leader on Monday.
Mr Brogden quit in disgrace following his admission that he had called former Premier Bob Carr’s wife, Helena, a mail order bride.
The comment was made at a function in July when Mr Brogden also sexually harassed two journalists.
Mr Carr has offered his support to Mr Brogden and said he should put the past behind him.
“Helena and I just want to send a message to John Brogden that he should look to his future,” said Mr Carr.
“As far as we’re concerned this incident is behind us, it should be behind him.”
“The world accepts that all of us makes mistakes and he’s got a big future as a politician, a member of his community and as a father of his son, Flinders,” he said.
The deputy Liberal leader, Barry O’Farrell, visited Mr Brogden in hospital at 2am and has since decided not to contend the leadership.
“Things like last night put all these things into perspective,” said Mr O’Farrell.
“It’s not about individuals and my decision today is not about me. It’s about what’s best, not just what’s best for the people of NSW and having a credible alternative government, but how the party can best deliver that.”
“And I’ve decided that I can’t deliver that unity… and I’ve got no right to put myself forward as leader.”
Mr O’Farrell’s decision leaves only one contender for the leadership, Opposition transport spokesman, Peter Debnam.
Mr Debnam says some doubt remains over whether a meeting concerning the new leader may not be held on Wednesday as planned.