Minority Leader Hakeem Jeffries of New York was the Democrats' choice for speaker.
"House Democrats are united behind the most powerful legislative leader in this chamber," said Rep. Pete Aguilar, D-Calif., of Jeffries.
With opposition from his GOP colleagues, Johnson arrived confident after working into the night to sway hardline holdouts.
"We don't have time for drama," Johnson said as he walked into the Capitol.
He received a renewed nod of support from Trump. "A win for Mike today will be a big win for the Republican Party," Trump posted Truth Social.
What was once a ceremonial day with newly elected lawmakers arriving to be sworn into office, often with family, friends and children in tow, has evolved into a high-stakes vote for the office of speaker, among the most powerful elected positions in Washington, D.C. Vice President Kamala Harris was swearing in the senators.