The announcement came after a high-level ministerial meeting in Nairobi on cooperation including on security, as well as trade and the movement of people.
"We have resolved that the border between Kenya and Somalia will be reopened in a phased manner within the next 90 days, effective today," Interior Minister Kithure Kindiki said, adding that a first crossing should be opened in 30 days.
The two nations had announced plans in July last year to reopen the frontier at talks between then Kenyan president Uhuru Kenyatta and his Somali counterpart Hassan Sheikh Mohamud but it never materialized.
Kindiki said they would work together on security, improving information sharing and mechanisms for cross-border collaboration.
"Kenya and Somalia are continuously experiencing both inter and intra-security challenges emanating from Al-Shabab," he added.
The frontier had been officially closed in 2011 because of attacks on Kenyan soil by Somalian Islamist militant group.
Kenya is a major contributor of troops to the African Union military operation against the Al-Qaeda-linked Al-Shabab, which has been waging a violent insurgency in Somalia for more than 15 years.
Relations between the two nations have been dogged by a maritime border row as well as Somali accusations of Kenyan meddling in its affairs, while Nairobi has accused Mogadishu of using it as a scapegoat for its own political and security problems.
Somalia severed diplomatic ties in December 2020 after Nairobi hosted the political leadership of Somaliland, a breakaway region not recognized by the central government in Mogadishu.
Kenya and Somalia share a 680-kilometer land border and have been locked in a long-running dispute for years over a potentially oil-and-gas rich chunk of the Indian Ocean.
In October 2021, the U.N.'s top court handed control of most of the area to Somalia but Kenya rejected the ruling.
