The increased number of UDPS seats, up from 35 in the 2018 election, along with gains by allied parties, could enable Tshisekedi to maintain his ruling big tent Sacred Union coalition, giving him the majority needed to name a new government.
The coalition controlled over 390 seats in the outgoing legislature.
Provisional results announced by DRC's national election commission early on Sunday showed that parties led by some of Tshisekedi's allies including Senate President Modeste Bahati Lukwebo, Defense Minister Jean Pierre Bemba and Economy Minister Vital Kamerhe won 35, 17, and 32 seats respectively.
The results of the legislative vote follow the Constitutional Court's confirmation of Tshisekedi's landslide re-election in the disputed December 20-24 general election that was marred by allegations of fraud, logistical shortcomings and disruptions.
Opposition parties and independent observers have raised concerns about the election's transparency, citing chaotic voting conditions and a murky tabulation process.
Several western governments made similar observations in congratulatory statements to Tshisekedi, who is set for another five years as leader of Africa's second-largest country after a first term hampered by economic woes and a security crisis in the eastern regions.
The fallout of the vote threatens to further destabilize DRC, the world's third-largest copper producer, and the top producer of cobalt, a battery component needed for the green energy transition.
DRC's opposition parties have repeatedly blasted the election as fraudulent and called for a re-run — a demand authorities have dismissed.
The electoral commission has defended the poll's credibility, although it invalidated votes cast for 82 of the 101,000 legislative candidates over alleged fraud and other issues earlier this month.
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