Christie said he made a commitment to the state of New Jersey and "it didn't feel right ... to leave before the job is done," but he isn't ruling out a future White House run.
"I believe in my heart this is where I belong," Christie told reporters at the New Jersey Statehouse.
The famously blunt, budget-cutting governor also told his constituents: "whether you like it or not, you're stuck with me."
Christie had spent the past few days reconsidering his long-time refusals to run for the GOP presidential nomination in light of encouragement from GOP leaders.
"I felt the obligation to earnestly consider their advice," he said. "Over the last few weeks, I've thought long and hard about this decision."
Ultimately, he decided against it on Monday evening.
"I went to bed last night for the first time in the last few days knowing exactly what I wanted to do," Christie said.
If he had run, he would have faced a challenge to quickly assemble a campaign just three months before voting begins. After months of waiting, Christie was far behind his rivals in fundraising and particularly in organizing on the ground in key early states like Iowa and New Hampshire.
His decision means the Republican race remains focused on two men - former Massachusetts Gov. Mitt Romney and Texas Gov. Rick Perry.
But a new national poll shows Perry's support dropping after weeks of defending his Texas record and businessman Herman Cain rising following a much-praised debate performance. The Washington Post-ABC survey shows former Massachusetts Gov. Mitt Romney regaining the lead, though his support remains in the same place it's been for months - the mid-20s.
The push for new candidates like Christie and the quick rise and fall of others - like Minnesota Rep. Michele Bachmann and real estate mogul Donald Trump, who also flirted with a presidential bid - reflect continued discomfort in the GOP with Romney. He has been steadily campaigning since he lost in the 2008 primary but hasn't been able to sway skeptical conservatives who make up the party base.
But while Tuesday's announcement ended the will-he-or-won't-he drama for now, his endorsement this year will still hold sway; he declined to back any of the declared candidates on Tuesday.
If Obama wins re-election, he'll likely be at the top of the list of presidential hopefuls in 2016.
The Associated Press contributed to this report.