John MacKillop travelled to New Zealand to join his father, who was looking for gold.
but New Zealand became his final resting place after a fall from a horse.
While his injuries were initially not considered to be life-threatening he contracted tetanus and died on December 7, 1867, age 22.
The Sisters of St Joseph knew MacKillop was buried in a Catholic cemetery somewhere in Christchurch but previous attempts to find him failed after early records were lost in a fire.
It was music teacher and former nun Mary Parker, 85, who eventually discovered his grave in the early 1990s.
Thanks to Ms Parker and the Knights of the Southern Cross, MacKillop's newly restored gravestone will be blessed on Saturday at his original burial site in the Barbadoes St Cemetery.
From a book of epitaphs from the Barbadoes St Cemetery, Ms Parker learnt that Mr MacKillop was buried beneath a tree there.
"I wandered all over the place and couldn't find it," she said.
She searched under almost all of the trees before approaching a "huge" one, with branches growing right down to the ground.
"I crawled under the branches and low and behold there it was."
Jill McLoughlin of the Sisters of St Joseph said the Knights of the Southern Cross in Christchurch recently took up the task of having the headstone restored.
"It was really covered in moss and in need of cleaning," said Sister McLoughlin.
She said the Knights, a group of men within the church, also had a plaque made stating that John was the younger brother of St Mary of the Cross.
Ms Parker said, "I think it means a lot to Christchurch."
Sister McLoughlin and Ms Parker believed St Mary spent time in the city, passing through on her way south to Arrowtown where she lived and ministered after the gold rush.
"To have her brother buried here is marvellous," said Ms Parker.