The move is in response to Judy Foote's announcement last week that she is leaving cabinet and intends to resign her seat in the House of Commons for family health reasons.
Kent Hehr is expected to move from Veterans Affairs to the Sport and Persons with Disabilities portfolio currently held by former Paralympic swimmer Carla Qualtrough.
Foote took a leave from the Public Works and Procurement portfolio in April; Natural Resources Minister Jim Carr has been doing double duty, filling in for Foote.
O'Regan's elevation to the cabinet will ensure a continued seat at the table for Newfoundland and Labrador, since Foote also represents the province.
The Public Works job is one of the toughest in the cabinet, responsible for handling the federal government's troubled Phoenix pay system as well as handling defence procurement challenges.
Trudeau - who has made gender parity in cabinet a big part of his government's identity - will likely tab a veteran to take over, meaning a rearrangement of several other portfolios. Adding O'Regan and losing Foote will upset the gender balance, barring other changes.
O'Regan, a former TV host, was first elected in 2015 and is a personal friend of the prime minister.
He and his partner were among the friends who accompanied Trudeau on a controversial family vacation last Christmas to a private island in the Bahamas owned by the Aga Khan, a billionaire philanthropist and spiritual leader of the world's Ismaili Muslims.
The previous Christmas, O'Regan spent the holidays in a “wellness centre” where he received treatment for alcoholism. He has openly discussed his struggles with alcoholism and mental illness.