A massive slip blocked the road in August last year, got worse in September and October, and crews had plenty of wet weather to contend with as they worked to clear the slip and repair the road.
Crews cleared about 370,000cu m of rock and debris, which a NZ Transport Agency spokesman said would have overflowed Wellington's Westpac Trust Stadium if it had been dumped there.
NZTA Palmerston North state highways manager David McGonigal said tired but relieved crew members had finished laying the road surface, painted fresh road markings, and were packing up the site.
The road re-opened to two lanes several weeks ago.
"The crew have stuck at the task for a long time, and they can now reflect on a job well done.
"They've rebuilt an entirely new piece of highway in a superbly orchestrated blur of activity, and words can't express the value of their hard work for the Manawatu region and beyond."
Mr McGonigal said half-bridge repairs had been completed just up the road from the main slip site and crews had also finished protecting the hillside with netting.
He said NZTA was grateful to the people of Manawatu and beyond for their patience, perseverance and understanding over the last 15 months.
While the job at the Manawatu Gorge was now finished, NZTA would continue its focus on improving the Saddle Rd.
"We recognise the importance of ensuring the people of Manawatu have peace of mind in the form of a solid alternative route.
"We'll be working closely with Tararua District Council and Palmerston North City Council on the rehabilitation and upgrade of the Saddle Rd.
"The Manawatu Gorge is a vital lifeline. While the last closure was an anomaly in terms of its scale and duration, the reality is that closures will happen from time to time, and we need to be ready."