Oli was also prime minister from 2015 to 2016, soon after the nation's current constitution was formalized.
This will be Oli's second stint as prime minister.
"The next Prime Minister KP Sharma Oli will be taking the oath this evening at 4 PM in Sheetal Niwas", Chetan Adhikari, Press Advisor for KP Oli informed ANI over Phone.
With the support from the CPN-Maoist Centre to the bid for premiership, Oli would now become prime minister under Article 76 (2) of the constitution.More news: Twitter trolls Manchester United as they lose to Newcastle
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"Oli is going to be pragmatic as prime minister to balance India and China", Kunda Dixit, editor of the weekly Nepali Times, told Reuters, though Oli's left-wing alliance is generally seen to lean towards China over India. His swearing in follows the resignation of Sher Bahadur Deuba from the post earlier in the day.
The swearing-in was held 69 days after the completion of elections to the federal and provincial assemblies.
The CPN-UML which had secured the majority amongst the parties in the Parliament has got the support from the Maoist Centre, with whom its talk for the merger is underway.
In 275 member House of Representatives, the lower house of parliament, Left Alliance secured an nearly two-thirds majority by winning 174 seats.
Deuba submitted his resignation in the morning after the country's election commission submitted the final results of the federal and provincial Assembly elections, which were held in December 2017, to the president.