Carter and his party were greeted at Pyongyang airport by top North Korean nuclear envoy Kim Kye Gwan, the North's official Korean Central News Agency said in a brief dispatch.
The dispatch gave no further details. U.S. officials had said late Monday in Washington that Carter would make the rare journey to North Korea to win the release of a 31-year-old sentenced to eight years in prison for entering the communist country illegally in January.
Aijalon Mahli Gomes, from Boston, was taken into custody after crossing into North Korea illegally from China.
North Korea agreed to release him to Carter if the ex-president made the journey to Pyongyang, a senior U.S. official told The Associated Press in Washington this week.
Carter was expected to spend one night in North Korea and return home with Gomes on Thursday, a second U.S. official said. Both spoke on condition of anonymity because of the sensitivity of the situation.
The senior U.S. official stressed that Carter was not representing the U.S. government but was on a private mission like the one former President Bill Clinton made a year ago to secure the release of two American journalists also sentenced for trespassing.
No U.S. officials were to travel with Carter, the official said.
South Korean media had reported that Carter was on a civilian jet with his wife, Rosalynn, and Carter Center President John Hardman. U.S. State Department spokesman P.J. Crowley said in Washington that he would not comment on Carter's trip.
"We will continue to withhold comment. We do not want to jeopardize the prospects for Mr. Gomes to be returned home by discussing any details related to private humanitarian efforts to get him released and back here safely to the United States," Crowley told reporters Tuesday.
Staff at the Atlanta-based Carter Center said they could provide no information.
North Korea is expected to portray Carter's trip - coming at a time of heightened tensions over North Korea's nuclear ambitions and the March sinking of a South Korean warship blamed on Pyongyang - as a diplomatic victory.
The Korean peninsula remains in a state of war because the 1950-53 Korean conflict ended in with an armistice, not a peace treaty. Washington does not have diplomatic relations with Pyongyang, and the U.S. military stations 28,500 troops in South Korea to protect the longtime ally.
When Bill Clinton traveled to North Korea to take journalists Laura Ling and Euna Lee home, Pyongyang's state media said Clinton apologized on behalf of the women and relayed President Barack Obama's gratitude during a meeting with North Korean leader Kim Jong Il.
It was not known whether Carter was scheduled to meet Kim on this trip.
It won't be Carter's first trip to the reclusive communist nation. The 85-year-old statesman made a historic trip to North Korea in 1994 when Bill Clinton was president - and met with then-leader Kim Il Sung - on a visit that led to a landmark disarmament deal on the Pyongyang's nuclear weapons program.
That deal alleviated tensions but fell apart in 2002 after the U.S. accused North Korea of having a secret uranium enrichment program. New, six-nation disarmament talks were launched in 2003, but Pyongyang walked away from the process last year.
Gomes, an English teacher from Boston who had been working in South Korea, was sentenced by North Korea in April to eight years of hard labor and fined $700,000 for crossing into the North illegally from China and committing an unspecified "hostile act."
It remains unclear why Gomes crossed into North Korea. However, Gomes had attended rallies in Seoul in support of Robert Park, a fellow Christian who deliberately crossed into North Korea from China to call attention to the North's human rights record.
Park was expelled from North Korea about 40 days after entering the country last Christmas.
U.S. officials have pressed for Gomes' release on humanitarian grounds, citing his health and reports that Gomes attempted suicide while in custody.
The pleas come amid a standoff over blame for the sinking of the South Korean warship that killed 46 sailors. Seoul and Washington blame Pyongyang for the incident; North Korea denies involvement.
Associated Press writer Matthew Lee contributed to this report from Washington.