"Politics shouldn't be a career and I never intended to make it one," Runyan said in a statement Wednesday. "While it has truly been an honor to serve the people of New Jersey's 3rd Congressional District, at this stage in my life, and more importantly, the lives of my three children, spending time with them is my top priority."
The former offensive lineman with the Philadelphia Eagles defeated a Democrat to win his seat in 2010, one of dozens of newcomers who lifted the GOP into the majority in the House.
Runyan, who has represented a central New Jersey district stretching across the state, was one of 87 Republicans to vote to reopen the government last month after the 16-day shutdown. He also is a co-sponsor of a House bill that would outlaw discrimination against gays in the workplace.
Runyan, who turns 40 at the end of the month, won his district with 54 percent of the vote in the 2012 election. Runyan's decision gives Democrats a chance to win back the seat.
"Jon came to Congress to help get our country back on track, and since Day One, he has been an important part of our efforts to reform the federal government and get reckless spending under control," said Rep. Greg Walden, R-Ore., chairman of the National Republican Campaign Committee. "While Jon will be missed, I wish him and his family all the best as they start the next chapter of their lives."