Former Auckland City mayor Christine Fletcher said Ryan was an "absolute stalwart" for his community.
He was someone who had a strong social conscience, she said.
"Frank was always there for the little guy. He was financially conservative, but that was not an excuse for forgetting those that were less advantaged."
Fletcher also acknowledged the support Ryan received from his wife. and said he would not have been the mayor he was without her support.
Meanwhile, Auckland mayor Phil Goff is mourning the death of his own father this week.
Bruce Goff died peacefully aged 96 at Elmwood Hospital on Wednesday, according to a notice in the New Zealand Herald this week.
Goff posted a series of photos of his father on his Facebook page this week, but has not spoken publically on his death
Bruce Goff 29/3/21 -5/7/2017 RIP
Posted by Phil Goff on Tuesday, 4 July 2017
A spokeswoman for the mayor said he did not want to comment on his father's death. A private funeral will take place on Tuesday.