Choe In-guk, the son of a South Korean ex-foreign minister who defected to the North with his wife in 1986.
Report informs citing the Israeli media, According to North Korean state media he will live in the North and work on reunification issues.
Mr Choe's arrival in Pyongyang was reported by the North's state media, which showed him being warmly received by North Korean officials.
He is cited on the North Korean propaganda website Uriminzokkiri as saying: "To live in and follow a country for which I feel thankful is a path to protect the will left by my parents.
"So I've decided to permanently live in North Korea, albeit belatedly."
Mr Choe frequently travelled to the North in recent years and attended his mother's funeral there.
His father Choe Tok-sin served as foreign minister of South Korea during the 1960s.
In the 1970s he emigrated to the US where he became a stern critic of the South Korea government under military leader Park Chung-hee.