Those arrested included Rep. John Lewis of Georgia, a leading figure in the civil rights movement in the 1960s, Rep. Charlie Rangel of New York and Rep. Jan Schakowsky of Illinois -- along with Joe Crowley of New York, Raul Grijalva of Arizona, Luis Gutierrez of Illinois, Keith Ellison of Minnesota and Al Green of Texas.
They were part of a larger group conducting a sit-in to block a street in the front of the Capitol, BuzzFeed politics reported.
The arrests came as thousands of protesters took part in the "Camino Americano: March for Immigration Reform" rally on the National Mall, even though the open-area national park is closed due to the federal government shutdown.
U.S. House Minority Leader Nancy Pelosi, D-Calif., told the gathering House Democrats support an immigration bill she introduced last week.
She said immigration reform could cut the federal deficit by hundreds of billions of dollars in the next 20 years because "immigration equals innovation," The Washington Post reported.
The bill closely matches a comprehensive bipartisan bill the Senate passed in June that includes a path to citizenship for most of the estimated 11.7 million immigrants living in the United States illegally. The House bill had no Republican sponsors.
Several House GOP leaders, including Judiciary Committee Chairman Bob Goodlatte of Virginia, said they hope to hold votes on smaller immigration bills in the next two months.
Julian Bond, a major figure in the civil rights movement in the 1960s, said "immigrant rights are civil rights."
"Immigration reform must come," he said. "It will come."
The National Park Service, which administers the mall, agreed to let the event take place under First Amendment privileges, rally spokeswoman Susana Flores told The Washington Examiner.
The First Amendment says Congress can make no law abridging free speech, peaceful assembly or an appeal to government to redress grievances.
The mall is intended to be the pre-eminent national civic space for public gatherings because it is considered the place where constitutional rights of speech and peaceful assembly find their fullest expression, a mall foundation statement says.
The 6-hour rally follows more than 150 rallies in 40 states Saturday.
Organizers described the Saturday and Tuesday rallies as their major show of strength this year.
Tuesday's rally -- which organizers said would attract "tens of thousands" of participants -- took place with the federal government shutdown in its second week and the Republican-controlled House locked in a feud with President Barack Obama and Democrats over healthcare and debt funding.
"I know there has been a shutdown, but we want Congress to know that the time is now to act," Evelyn Servin, an immigrant advocate, told The New York Times in Birmingham, Ala., during that city's rally Saturday.
About 30 members of Congress were expected to attend the Washington rally, including Rep. Luis Gutierrez, D-Ill., and Sen. Robert Menendez, D-N.J., organizers said. Organized labor and religious leaders also participated.
After the rally, demonstrators were to march to the U.S. Capitol, on the opposite end of the mall from the Lincoln Memorial.
The rally was hosted by several immigration activist groups, together with the National Education Association, National Hispanic Foundation for the Arts, Service Employees International Union and the AFL-CIO.