Ibrahim Adan Omar, who had a KES1 million ($13,500) bounty on his head, was nabbed at Bangali in Tana River County on Sunday.
An AK-47 rifle, two magazines and 100 rounds of ammunition were recovered from the suspect, the Daily Nation reported.
A major special forces air and ground operation has been ongoing since November 20, when Romano, a volunteer for the NGO African Milele Onlus, was kidnapped in an armed attack in the coastal town of Kilifi.
Omar is reportedly in custody and assisting police in their investigation.
Two other suspects – Yusuf Kuno Adan and Said Adan Abdi – are wanted in relation to the kidnapping are still on the run.
The suspects are believed to be planning to cross over into Somalia with Romano.
Police have offered a reward of around $13,350 to anyone providing information which may assist in the case.
