Barnaby Joyce and his partner Vikki Campion are expecting a second child.
The former Nationals leader and his ex-staffer Ms Campion have revealed the news to family and friends, The Courier-Mail reports.
"We are actually having another child, called Tom, so there you go," Mr Joyce said in footage broadcast by Seven News from a fundraiser on Sunday afternoon.
He apologised for Ms Campion's non-attendance at the event before breaking the news of his "great blessing".
It is understood the baby boy is due in June and will take the name after Mr Joyce's grandfather, Thomas.
The New England MP resigned as deputy prime minister and Nationals leader last February after revelations surfaced of his affair with Ms Campion.
The couple already have a baby son, Sebastian, and Mr Joyce has four daughters from his marriage with now estranged wife Natalie.
Opposition Leader Bill Shorten congratulated Mr Joyce and his family.
"That's entirely a personal matter for them and I congratulate them. Whenever a child is to be born it is good news," Mr Shorten told reporters in Queensland on Sunday.
Prime Minister Scott Morrison also offered his congratulations.
Australian Associated Press