The meetings will take place in October at a mountain resort in North Korea.
The decision follows an agreement last month that de-escalated tensions sparked by a border mine explosion that injured two South Korean soldiers.
Thousands of Korean families have been separated with little or no contact since the war ended in 1953.
The highly emotional reunions of family member who have not seen one another in decades have been infrequent, and depend hugely on the state of relations on the peninsula.
The BBC's Stephen Evans in Seoul says the reunions, which started in 1988, used to be annual but have often been cancelled in recent years as relations frayed. The last round was held in February 2014.
About 66,000 South Koreans remain on the waiting list to see their relatives, many in their 80s and 90s, our correspondent adds.
The upcoming reunions, slated to be held at the Diamond Mountain resort in Mount Kumgang from 20 to 26 October, will see 100 people from each side selected.
Source: Korea Red Cross
The decision came after Red Cross officials from both countries held talks earlier this week at the border village of Panmunjom.
Communication between relatives across the border is highly restricted and almost non-existent. The two countries remain technically at war as the Korean War ended with an armistice.

In a statement on Twitter, the band said it was "with great regret, due to illness, we cannot perform at Customs House Belfast".
Organisers said they were working to re-schedule the concert.
Many concert goers said they were disappointed with the last-minute cancellation.
Stephen Nelson said the stage was set-up for the band when the news was announced to the audience.
"They had set up everything, all the gear, their background was up, their roadies were on stage.
"Then 10 minutes before an announcement came on the PA that the gig was cancelled.
"People were like, 'are you serious?' Then the announcement was repeated and there was some booing."
Kathryn McKeown said the crowd were "disappointed" when the announcement was made.
"It was lashing rain on and off, everyone was drenched. Blossoms (the support band) were saying, 'are you excited for Kasabian?' before they finished.
She added: "About 10 minutes before the band were due on stage there was an announcement to say that due to last-minute illness the band would be unable to perform, tickets would be valid for a re-scheduled show.
"At first, I think everyone thought it was a joke. After about the third announcement it started to sink in and everyone started booing, some people were even chucking pints and plastic cups at the stage."
In a statement, organisers said: "Due to a last-minute illness we regret that the band have had to cancel tonight's show.
"We are working at this minute on scheduling a new date for Belfast. We will communicate with all ticket buyers via Ticketmaster and on the Custom House Square social media.
"Tickets will remain valid for the new date. We apologise for any inconvenience caused."
The band were due to play as part of a series of concerts at Custom House Square.
North and South Korea have agreed to hold rare reunions for families separated by the Korean War, according to Seoul.
[NEXT_CONCEPT]
Rock band Kasabian have cancelled a concert in Belfast minutes before they were due to take to the stage on Tuesday night.