Police had registered cases against six persons, including the councillor Vatsala and her husband Varatharaj in connection with the murder of the realtor Arumugam at the councillor's house on March 26.
Five including the councillor had been arrested while Varatharaj was absconding.
On information that Varatharaj was waiting near G N Mills bus-stop, police took him into custody. He is being interrogated, police said.
The realtor, hailing from Tirupur, had gone to the house of the councillor, in connection with a property deal and was allegedly beaten to death after some argument.