Registered psychologist Marcel Saxone was banned from treating clients following allegations made against him by the woman in August 2018.
He has been suspended since September that year after saying he didn't plan to return to practice.
But throughout investigations into the matter, Mr Saxone said the woman fabricated the claim that their relationship had a sexual element, adding that she was lying because he rejected her advances towards him.
He told the Victorian Civil and Administrative Tribunal she was "manipulative and prone to jealousy and rage, particularly when things did not go her way".
The woman told the tribunal the pair had engaged in consensual sex acts but did not have intercourse.
A panel of three tribunal members in April found Mr Saxone's conduct "involved multiple breaches of the boundaries".
The matter was referred to tribunal by the Psychology Board of Australia in September 2020.
The former psychologist conceded to providing substandard care and failing to keep adequate clinical records.
Mr Saxone, who represented himself, maintained that all of the allegations relating to sexual activity with the woman were "made up and a lie".
Among witnesses to give evidence were the woman's psychologist friend and her husband, who was also once a client of Mr Saxone.
The woman and Mr Saxone exchanged more than 700 emails over a nearly four year period, including many sent after hours and on weekends.
Those emails traversed a wide range of topics, many of which concerned non-clinical matters.
They also communicated by telephone and text messages.
The tribunal upheld the four allegations against Mr Saxone and a further hearing on the matter will be held at a later date.
According to his LinkedIn profile, Mr Saxone now works as a pastoral care worker in aged care.
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