The dictator boarded his armoured train at train at the Dong Dang border station ahead of a 2,500-mile rail journey through China to Pyongyang, expected to take two and a half days.
Talks between the two countries ended abruptly on Thursday, with Trump saying Kim had demanded that all sanctions be lifted in return for giving up some of his nukes.
But the North Korean side said they had only pushed for the lifting of some.
Both Trump and Secretary of State Mike Pompeo said there was a willingness on both sides to keep talking, but no follow-up summit has been scheduled.
North Korean leader Kim Jong-un left Vietnam today after his summit with president Donald Trump ended without a nuclear deal
The dictator boarded his armoured train at train at the Dong Dang border station ahead of a 2,500-mile rail journey through China to Pyongyang
Kim happily waved to crowds at the station in Vietnam today, having earlier paid tribute to Vietnam’s late revolutionary leader.
His trip to Vietnam was the first by a North Korean leader since 1964, when Kim Il Sung also travelled by rail for his journey to the southeast Asian nation.
Kim had made a highly unusual stop at the stark concrete monument where the body of Ho Chi Minh is on display.
On historic anniversaries Kim regularly pays tribute to his own predecessors, his father Kim Jong Il and grandfather Kim Il Sung, at the sprawling memorial palace on the outskirts of Pyongyang where their preserved remains lie in state.
But he is not known to have previously done anything similar for a foreign leader.
The North Korean adjusted the ribbons on a large wreath emblazoned with his name and the message ‘Cherishing the memory of President Ho Chi Minh’ before bowing his head for no less than 48 seconds.
Talks between the two countries ended abruptly on Thursday, with Trump saying Kim had demanded that all sanctions be lifted in return for giving up some of his nukes
Kim has visited China, the North’s key diplomatic protector and main provider of trade and aid, four times but there have been no reports in either country’s state media of him going to Mao Zedong’s mausoleum in Beijing.
But Kim’s grandfather was a close friend of Ho Chi Minh and supplied him with fighter pilots and psychological warfare specialists during his war against the US-backed regime in South Vietnam.
Pictures of the two together are displayed on the noticeboard outside the Vietnamese embassy in Pyongyang.
Kim’s route through China is not known and it was not clear whether he would be stopping to meet President Xi Jinping along the journey.
A smiling Kim waved to crowds at the station and clasped his hands in the air as he was seen off by white-uniformed soldiers and Vietnamese officials.
‘I really admire Chairman Kim Jong Un and I see him as a friendly person,’ said local resident Nguyen Thuy Chi at the station.
On Friday Kim met Vietnam’s top leaders and reportedly tried his hand at playing a dan bau – a traditional single-string guitar.
Pictures in the Vietnamese press showed the grinning leader with the instrument as a crowd of Vietnamese guests – including President Nguyen Phu Trong – cheered him on.