Devenport leaves on September 21 and admits she is looking forward to the new opportunities that lie across the Tasman.
However, she said she still remains "a strong and enduring advocate" for Auckland Art Gallery.
"I have learned a tremendous amount during these five years and have been impressed daily by the astounding levels of professionalism and commitment of my team.
"I am proud of what I have achieved during this time and have enjoyed making what I trust will be seen as a lasting and positive contribution to the gallery's success and future," she said.
Recently the art gallery has struggled financially and Auckland Mayor Phil Goff has proposed a boost in funding.
Goff said it was a critical asset to the city and proposed a $20m funding boost inside the council's 10-year budget.
The move followed growing concerns about the gallery's operating budget being progressively cut from $12 million in 2012 to $6.9m.
Brooks extended his thanks to Devenport for all the effort she had put into her five years with the gallery, wishing her success in the future.
"With strong visitor numbers and world-class exhibition programmes, Rhana has made a lasting contribution and helped to cement Auckland Art Gallery Toi o Tāmaki as a cultural leader that truly strengthens and enriches our communities," he said.