The project included restoring an 112-year-old stencilled frieze uncovered in January last year.
The lodge dates back to 1878 and the building in Berkshire St was completed and officially designated as "Lodge Arrow Kilwinning No 86" on January 23, 1888.
The lodge room was plastered and a dado railing installed in 1898.
It is believed the wall paintings also date back to this time.
However, they were covered up and forgotten when the room was lined with Pinex sheets and repainted in the 1940s or '50s.
Architect and historic buildings specialist Jackie Gillies has been leading the restoration project.
She discovered the stencilled frieze beneath the painted Pinex walls.
The dado-level frieze repeats square-and-compass motifs between single stars, in dark reddish-brown paint, with gold highlights.
At cornice level, hand-painted swags of drapery were found, with additional Masonic motifs meeting at each corner of the room in large painted tassels.
A large gold-painted square-and-compass insignia was uncovered on the chimney breast on the south wall and a silver moon and stars were found on the east wall.
A black and white tessellated pavement, painted on to a floor canvas with symbolic objects painted on it, was uncovered in the centre of the room.
"The paintings were considerably damaged in places by the crude cutting-in of timber battens along the top and bottom of the wall, and the historic lime wash base coat had suffered from its long enclosure," Ms Gillies said.
Historically faithful replastering and retouching began, using the only intact wall in the room as a guide.
Wall painting restorer and conservator Eimear O'Connell, from Ireland, spent four weeks repainting the motifs, symbols and decorations.
The $220,564 restoration was funded by the Heritage Lotteries Fund, Central Lakes Trust, Community Trust of Southland and the Arrowtown Heritage Trust.
It also involved structural repairs, completed by builder Martyn Smith, including strengthening the roof and upgrading the heating and lighting.
Mason Blair Rodger said the dramatic paintings were very rare.
It is not known if others exist in New Zealand, but the Arrowtown designs are the only ones in the South Island.
He said the project began in 2003 and it took over six years to get resource consent, funding and complete the restoration work.
He said the 20 Arrowtown masons were delighted it had finally been completed.
A DVD has been produced by Digital Dog Ltd to record the restoration project and it will include the history of the lodge and Arrowtown.
The lodge will be rededicated at a ceremony on Saturday and about 100 masons are expected to attend.
An opening for the public would also be held at the weekend, he said.
