The appointment of Mr Ng Chee Meng and Dr Koh Poh Koon as the labour movement's deputy secretaries-general comes ahead of a Cabinet reshuffle, which Prime Minister Lee Hsien Loong said last night will happen in a day or two.
PM Lee also said in his Facebook post that he has asked labour chief Chan Chun Sing to return to the Government.
Mr Chan, who has been secretary-general of the National Trades Union Congress (NTUC) for three years, looks set to take on another ministerial role. He is a leading member of the fourth-generation of People's Action Party leaders.
When he leaves, Mr Ng is expected to step into his shoes and helm the NTUC.
No date of this potential move has been set, with PM Lee disclosing only that Mr Ng will begin serving the labour movement full time on May 1.
The NTUC Central Committee can appoint a new secretary-general at any time.
But at the next union election, the secretary-general has to stand and win the necessary votes to be elected into the committee to keep his position.
Union elections are held every four years, with the next one taking place some time next year.
At the election, union leaders vote by secret ballot for the 21 members of the Central Committee. The committee members will then decide among themselves who will be the secretary-general.
Mr Chan joined the labour movement in January 2015, also as a deputy secretary-general. He was promoted to secretary-general, replacing outgoing chief Lim Swee Say, in April the same year.
With the appointment of Mr Ng and Dr Koh, NTUC now has three deputy secretaries-general.
The third is Mr Heng Chee How, who has held the position since 1999.
This is the first time the NTUC has co-opted and appointed at the same time two deputy secretaries-general.
Its president Mary Liew said the move shows NTUC is going through "a lot of changes and challenges".