But an analyst played down Monday's restoration as a "symbolic" gesture, noting the North's recent missile launches.
"Even if this leads to talks, we may enter a new phase where North Korea engages in dialogue but continues to carry out provocations simultaneously," said Park Won-gon, a professor of North Korean Studies at Ewha Womans University.
The North has often unilaterally suspended the hotlines and reactivated them when it needed better ties with its southern neighbour.
North Korean liaison officers on Monday answered phone calls by their South Korean counterparts over a set of cross-border government and military channels for the first time in nearly two months.
"Long time no talk. We're very pleased because the communication channels have been restored like this. We hope that South-North relations will develop into a new level," a Seoul official said during a phone conversation with his North Korean counterpart over one channel, according to video released by South Korea's Unification Ministry.
It did not carry the voice of the North Korean.
On a separate military channel, the Koreas exchanged information about fishing activities along their disputed western sea boundary - where several inter-Korean bloody naval battles have occurred in previous years - to prevent similar skirmishes, Seoul's Defence Ministry said.
A ministry statement said Seoul hopes the hotlines' restoration would help reduce tensions on the peninsula.
The hotlines are phone and fax channels the Koreas use to set up meetings, arrange border crossings and avoid accidental clashes.
They have been largely dormant for more than a year after the North cut them off in protest at South Korean civilian leafleting campaigns.
Communications were briefly revived for about two weeks in recent months, but North Korea again refused to exchange messages after Seoul staged annual military drills with Washington that Pyongyang views as an invasion rehearsal.
Last week, North Korea leader Kim Jong-un expressed willingness to reactivate the communication channels, saying he wanted to realise the Korean people's desire to promote peace on the peninsula.
Some experts question the sincerity of North Korea's overture, which came as the nation renewed missile tests after six months.
The president's influential sister, Kim Yo-jong has also said South Korea must abandon "double-dealing standards" and a "hostile viewpoint" if it truly wants improved ties.
Observers say North Korea is trying to use the South's desire to improve ties to pressure it to convince the United States to relax punishing economic sanctions.
"The South Korean authorities should make positive efforts to put the North-South ties on a right track and settle the important tasks which must be prioritised to open up the bright prospect in the future, bearing deep in mind the meaning of the restoration of communication lines," the North's official Korean Central News Agency said ahead of the hotline's restoration.
Additional reporting: AFP