Khoso, 84, belongs to Goth Azam Khan Khosa in Jaffarabad district of Balochistan province and earlier served as chief justice of both the Balochistan high court and the Federal Shariah Court.
After the prime minister and leader of opposition and a bipartisan parliamentary committee were unable to choose a caretaker premier after six days of deliberations, the matter was sent to the five-member election commission on Friday night.
Following two days of discussions, Chief Election Commissioner Fakhruddin G Ebrahim announced this afternoon that the poll panel had chosen Khoso for the slot.
He said one member of the panel had given a dissenting vote.
The member from Punjab province, nominated by the main opposition Pakistan Muslim League-Nawaz, opposed Khoso’s candidature.
The PML-N had earlier expressed its reservations about Khoso, saying he was considered to be close to the Pakistan People's Party, which led the outgoing government.
Khoso was among four candidates for the post of caretaker premier.
While the PPP and its allies nominated Khoso and banker Ishrat Hussain, the PML-N proposed retired judge Nasir Aslam Zahid and Sindhi politician Rasool Baksh Palejo.
Chief Election Commissioner Ebrahim told reporters: "We discussed the candidates at length and slowly because it is a very important issue. This gentleman is going to hold free and fair elections along with us."
A law graduate from KarachiUniversity, Khoso was appointed as a judge of the Balochistan high court in 1977.
He went on to serve as chief justice of the high court during 1990-1991 and as chief justice of the Federal Shariah Court in 1994.
Khoso's first political appointment was as acting governor of Balochistan.
Pakistan to hold general election on May 11
Ashraf proposes names for caretaker PM ahead of Pak polls
Pak: Qadri approaches SC, seeks restructuring of EC
Do not fall into the Pakistani military's trap
Pak Taliban wants A Q Khan as guarantor in talks with govt