"Our sleuths arrested Rushikesh Devdikar from Katras in Jharkhand's Dhanbad district on Thursday," a Special Investigation Team (SIT) official told here.
Katras is about 140km northeast of Jharkhand's capital Ranchi.
Devdikar, 44, was absconding since September 5, 2017, when the 55-year-old Lankesh was gunned down in front of her house here in the southwest suburb.
"The 18th accused is being brought to the city from Jharkhand for judicial remand and investigation into his role in Gauri's killing," said the official.
"A search is underway at Devidkar's his house in the city for documentary or material evidence as was primarily involved in the conspiracy to kill Gauri, who was also a social activist," chief investigation officer M.N. Anucheth said.
The SIT, which was set up by then state government within days after the gruesome incident to hunt down Lankesh's killers, arrested Devidkar.
Lankesh was the editor of the weekly Kannada tabloid "Lankesh Patrika", founded by her late father and eminent journalist Lankesh. She also worked earlier as Karnataka correspondent in the defunct "Sunday" magazine and "The Times of India" in Bengaluru.
The SIT has so far arrested 17 suspects, including Ganesh Miskin, who is alleged to have shot at Gauri from a close range after riding to her house on a motor bike with an accomplice.
The SIT has filed two charge sheets under the Karnataka Control of Crimes Act in the case in November 2018 and May 2018 in the special court, set up to conduct the trial on fast track basis.
Miskin was also the alleged hitman in the murder of noted Kannada writer M.M. Kalburgi at Dharwad in the state's northwest town in August 2015.
( With inputs from IANS )