McCarthy's district is expected to remain in Democratic hands. President Obama won there by 13 percentage points in 2012.

McCarthy has not voted since early June, when she announced she would be taking a leave of absence to be treated for lung cancer. She has made few public appearances since, but appeared briefly in December at an event commemorating the 20th anniversary of the Long Island Railroad shooting. Her husband was killed in the attack and her work in gun control compelled her to later run for Congress.

McCarthy's chief of staff and communications director have departed in recent months, which suggested to close observers that she was planning to step down.

McIntyre and McCarthy become the 11th and 12th members of the House to announce their retirement in 2014.

The news of the two retirements was first reported by Politico.

First elected in 1996, McIntyre barely held onto his job in 2012, defeating Republican David Rouzer by only about 700 votes. His district was redrawn during the decennial redistricting process, making it more conservative. He sits in one of the most conservative districts represented by a Democrat. Rouzer is running for the seat again this year.

McIntyre often bucked his party, even voting against the federal health-care law. Republicans said his decision is a sign that not even Democrats who have opposed the law are insulated from its problems.

"If it wasn’t clear before with the retirement of Rep. Jim Matheson, today’s announcement from Rep. Mike McIntyre solidifies the extremely difficult road ahead for Democrats in 2014," said National Republican Congressional Committee Chairman Greg Walden (Ore.).

In a statement, McIntyre thanked his family, staff and colleagues for working with him throughout his tenure.

"My family and I are ready for a new chapter and excited about new opportunities to continue helping North Carolina," he said.

Also first elected in 1996, McCarthy is arguably best-known for being an outspoken advocate of stricter gun laws.

"Carolyn's successor will have big shoes to fill," said Democratic Congressional Campaign Committee Chairman Steve Israel (N.Y.). "We are confident that the people of this strongly Democratic seat will choose a replacement who will follow Carolyn’s tradition of putting middle class families first and fighting for the safety of our schools and neighborhoods."

Updated at 2:59 p.m.