During the massage, the therapist then placed one hand in his trousers and touched himself while he continued to massage the woman with his other hand.
The woman heard the sound of the man touching himself and she turned around to confront him.
As the woman left the room, he offered her a refund, which made her more upset, the decision says.
The man later pleaded guilty and was convicted of indecent assault at Auckland District Court in 2014.
Last year, he wrote a letter to the tribunal’s executive officer.
In it, he said he "deeply regretted" his actions.
He also wrote about his struggles of finding a full-time job because of his conviction.
The hearing found the case was serious in nature and constituted a "gross breach of trust".
"It involves a practitioner who unquestionably breached the trust of the person with whom he was dealing in an environment which, although not clinical, was very similar in its nature," the decision stated.
However, it noted he was convicted and punished through the justice system, and therefore his punishment was of a lesser degree than it otherwise may have been.
He was fined $2250 and his practising certificate suspended for six months and ordered to be supervised with patients.