It was not yet confirmed whether Dr O'Sullivan would stand in an electorate or stand as a list member.
However, Mr Flavell said during the Tauranga hui the Maori Party had an agreement not to stand a candidate in the Te Tai Tokerau electorate against Mr Harawira.
Mr Flavell said he was pleasantly surprised by Dr O'Sullivan's announcement because although he had expected the decision, he did not know it had yet been confirmed. He was excited about Dr O'Sullivan's standing and looked forward to what he could bring to the party.
"We've been pushing for a while," Mr Flavell said.
"He's put his hand up which we're extremely pleased about," he said.
He said Dr O'Sullivan had plenty to offer, particularly with his expertise and passion in the medical field.
"He brings a huge credibility as New Zealander of the Year.
"He'll be a great asset."
Dr O'Sullivan's passion for health is undeniable.
He is the the founder of iMOKO, a digital healthcare programme making healthcare more accessible to New Zealanders, a vocal supporter of vaccinations and a man who has worked to improve health in the Far North and received many accolades for his efforts in the health industry.
His confdence for the Maori Party is also evident, having supported the group since its inception.
Dr O'Sullivan said he wanted to ensure the party's health well into the future and planned to enter the 2020 election with strong merits.
He is working with his former school Hato Petera College, which is due to close next year, to ensure its revitalisation and resurgence and working to make sure people can access health advice digitally for faster treatment - all before 2020.
