The changes will be made at Rideau Hall at 11 a.m. ET. The Prime Minister's Office issued an advisory around 8 p.m. Sunday night for the event.
"[It] will be a substantial and significant shuffle," a source told CBC's Evan Solomon, host of Power & Politics and The House. "There will be new faces and younger members alongside experienced and capable hands."
The source also said there will be new women in cabinet and that the government's focus will remain on the economy.
Some have speculated that Finance Minister Jim Flaherty might be among those moved but CBC News has learned he will not be changing jobs. Foreign Affairs Minister John Baird is also staying put.
There will be a new public safety minister, however, following the resignation of Vic Toews who quit politics last week.
There will also be a new fisheries minister — Keith Ashfield has cancer and asked Harper to relieve him of his duties in the next cabinet makeover.
A recent message on Environment Minister Peter Kent's Facebook page signalled that he could be out, and said he would have no problem making way for a younger cabinet member in his job.
The intergovernmental affairs portfolio also needs a new minister since Peter Penashue resigned over ineligible campaign contributions from the last election. He ran and lost in the byelection in the wake of his resignation and his cabinet duties were taken over by Transport Minister Denis Lebel.
Lebel is the lead minister handling the Lac-Mégantic train disaster.
Junior finance minister Ted Menzies and Diane Ablonczy, the minister responsible for consular affairs, both indicated in recent weeks that they would not be running in the next election in 2015, which means Harper will likely not keep them in cabinet.
The Canadian Press reported that Ray Novak, Harper's chief of staff, began phoning ministers and cabinet newcomers with their new assignments on Saturday night.