Mr Callaghan was a council employee from 1971 until 1993.
Long-serving councillor Trevor Maxwell shared the mayor's sentiments describing Mr Callaghan as "a warm-hearted guy" who had a great love of rugby, especially Bay of Plenty rugby.
"In his role at council he was very approaching and very inclusive and he was a huge support for anyone dealing with council at the time – he was the go-to if iwi had any issues or problems and played a huge role at council," Maxwell said.
Former Rotorua mayor Grahame Hall said Callaghan was employed by the former County Council and when in 1979 it amalgamated with the then City Council to become the district council, he transferred to the new local body.
Hall said Mr Callaghan provided great support and advice for former mayor, the late John Keaney, and to all elected members.
"He was very, very well respected, a really great guy who had a passion for what he was doing. He was always really good at getting out amongst the people and was the first port of call if there was an issue.
"Being a good strong community man, even in his work for council he always had the community at heart and did everything on the basis of what was good for everyone."
Hall said he remembered his great sense of humour and said he tried to keep himself fit and in shape.
"I used to see him running the streets in the mornings. He was someone who earned huge respect from all local elected members, as well as council staff and iwi," Hall said.
Perenu Kaingakau Callaghan's funeral service is at St Faith's Church, Ohinemutu, at 11am Thursday May 17.