"It's been one of the most emotional days of my life," he told Newstalk ZB.
"My major emotion really is relief and now it's time to just make memories with my father and my family."
Formerly describing himself as "completely nauseous" due to dehydration, Lehndorf said his first glass of water was "pretty delicious".
Lehndorf said others impacted by New Zealand's MIQ system could rejoice in the outcome.
"This is a win not just for me, but for everybody out there who's had to endure what I feel is a pretty huge injustice."
An MIQ spokesman said he was glad Lehndorf could reunite with his family.
"We are pleased this means he will be able to spend time with his father at this difficult time."
It came after a tumultuous time in MIQ when, even to this morning, Lehndorf wasn't sure whether he would be released.
Lehndorf earlier said his most recent communication was with a nurse last night who told him his day 3 PCR test for Covid-19 had come back negative, and that he was being offered "temporary visitation" to see his dad, but he said he did not know what that meant.
He had believed it would mean getting picked up by a security guard, driven to his father's property and given a period of time to spend with his dad.
That uncertainty was paired with the consequences of his hunger strike, which had left him feeling "dreadful" and "broken".
In three weeks' time people in Lehndorf's position will be able to fly in from Australia and self-isolate immediately.
Late last night the MBIE, which runs MIQ, confirmed to Newstalk ZB that Lehndorf's day 3 test was negative, and said arrangements would be made for him to see his father.
"The compliance letter has been prepared for Mr Lehndorf, which states the conditions of this exemption - for example, details related to travel arrangements, people permitted within the household, and timing.
"This will be provided to Mr Lehndorf imminently, and arrangements will be made for him to see his father.
"All returnees in our care are provided with appropriate health and wellbeing support while in isolation. He will continue to have all meals delivered, and his health and wellbeing will be closely monitored by health staff."