Federal Nepal, 2015–2025
Sushil Koirala resigned as prime minister on 10 October 2015 after losing support from CPN (UML). Nepali Congress joined the government again in August 2016 under the leadership of Bimalendra Nidhi, after backing Pushpa Kamal Dahal to become prime minister. According to their agreement, Dahal resigned on 24 May 2017 paving the way for Deuba to become prime minister for a fourth time on 6 June 2017.
On 22 April 2017, the Akhanda Nepal Party led by Kumar Khadka joined the Nepali Congress ahead of the 2017 local elections. Nepali Congress won 11,456 seats including 266 mayoral or chairman positions. The party also won mayor posts in Lalitpur and Biratnagar. Ahead of the 2017 general and provincial elections, Nepal Loktantrik Forum led by former Nepali Congress leader, Bijay Kumar Gachhadar merged into the party. Similarly, a group from Federal Socialist Forum, Nepal led by MP Abhishek Pratap Shah, a group from CPN (UML) led by MP Mohar Singh Rathore and Rabin Chaudhary, a goroup from Rastriya Janata Party Nepal led by MP Jangi Lal Ray, a group from CPN (Maoist Centre) led by former Minister and MP Sambhu Lal Shrestha joined the party ahead of the 2017 election.
The party won 63 seats to the House of Representatives becoming the second largest party. The party could win only 23 seats under first past the post and many influential leaders including Ram Chandra Poudel, Ram Saran Mahat, Bimalendra Nidhi, Krishna Prasad Sitaula, and Arjun Narasingha K.C. lost in their constituencies. The party won 113 seats in provincial assemblies and became the largest opposition in six out of seven provinces. Following the 2018 National Assembly election, Deuba resigned as prime minister. Deuba was challenged for the leadership of the parliamentary party by Prakash Man Singh following a disappointing performance in the electionb but defeated his opponent 44–19.
Nepali Congress remained as the main opposition party until a split in the ruling Nepal Communist Party in 2021. The split occurred following an attempt to dissolve the House of Representatives. The party opposed the move and the decision was scrapped by the Supreme Court. Another attempt to dissolve the House of Representatives was quashed again by the Supreme Court and Nepali Congress president Sher Bahadur Deuba was appointed prime minister with the support of CPN (Maoist Centre) and CPN (Unified Socialist). The party also joined the provincial governments of Karnali, Province 2, Gandaki and Lumbini. The party headed governments in Gandaki and Karnali during this time.
The party held its 14th general convention from 13 to 15 December 2021. The party announced an active membership of 850,000 members and Sher Bahadur Deuba was re-elected as party president in the second round. The party elected Purna Bahadur Khadka and Dhanraj Gurung vice-presidents of the party, while Gagan Thapa and Bishwa Prakash Sharma were elected as general secretaries.
The party contested the 2022 elections with an alliance with their coalition partners CPN (Maoist Centre), CPN (Unified Socialist) and other smaller leftist parties. In the 2022 local elections, the party won executive head positions in 329 local units including in the metropolitan cities of Lalitpur and Biratnagar. In the general elections that followed, the party won a plurality of seats in the House of Representatives and in provincial assemblies of Bagmati, Gandaki, Karnali and Sudurpaschim.
The resulting government saw Congress in the opposition again following a breakdown in the alliance. Another alliance change saw Congress joining the coalition government of CPN (Maoist Centre) in March 2023 before again joining the opposition bench in March 2024. The party forged a deal with CPN (UML) in July 2024 to form a new coalition government under CPN (UML).
The coalition government introduced a mandate to shut down social media for failing to register with the government which served as the trigger for the 2025 Gen Z protests. Following the death of 19 protestors as a result of the use of live ammunition, home minister Ramesh Lekhak from the party resigned, other ministers also resigned the next morning, but protestors vandalized the party headquarters and other local offices of the party across the country. Party president Sher Bahadur Deuba was assaulted at his residence along with his wife and foreign minister Arzu Rana Deuba. The houses of other leaders of the party were also vandalized and set ablaze. The government also resigned following the protests.
