South Korea's presidential Blue House and North Korea's State Affairs Commission tested the hot line for four minutes before South Korea's Moon Jae-in and North Korea's Kim Jong Un talk ahead of next week's summit, the office said.
"The call quality was very good and we felt like we got a call from our next-door neighbour," South Korea's director for the Government Situation Room, Youn Kun-young, told reporters.
Moon will now be able to pick up his office phone to talk to Kim, instead of communicating through a hot line at the Joint Security Area in the border village of Panmunjom.
The plan was unveiled by the South's National Security Adviser, Chung Eui-yong, after he met Kim last month in Pyongyang.
Impoverished North Korea and the rich, democratic South are technically still at war because their 1950-53 conflict ended in a truce, not a peace treaty and the North has been engaged in a standoff over its nuclear and missile programmes that it conducts in defiance of UN Security Council resolutions.
But tensions have eased in recent months, with the North taking part in the Winter Olympics in the South in February and an exchange of threats of war with the United States and other bellicose rhetoric evaporating.
Now North and South Korea are meeting next week and Kim and US President Donald Trump are expected to hold their first ever summit in May or June, with denuclearisation the topic of the day.
The system reportedly features a telephone, a fax and a screen with Internet connection for a video chat.
Lim Dong-won, a key architect of the late liberal president's Sunshine policy of re-engagement with the North, said in his 2007 memoir that the phones played a critical role in resolving sensitive issues.
The communication channel was also used by Roh Moo-hyun, the successor to Kim Dae-jung, until the conservative Lee Myung-bak took over in 2008, Seoul officials said.
There was no communication at Panmunjom as the standoff deepened over Pyongyang's weapons programmes, until the hot line was used for the first time in nearly two years in January.
During the lull, South Korean officials would sometimes use a bull horn to shout messages across the border.
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