It was unclear whether the 60 year old resigned or was sacked and NZC declined to make any additional comment after releasing a diplomatically-worded statement.
"Buchanan, who took up the role at NZC in May 2011, is disappointed to be leaving NZC at this time as he has enjoyed his work there," it read. "However due to family circumstances, he has decided to return to Australia.
"NZC respects John's decision to return home and we wish him well for his future endeavours."
Buchanan, who led Australia to two World Cup victories, was given an over-arching role in New Zealand's high-performance programme, causing friction with previous team coach John Wright.
Local media have also reported that Buchanan had a difficult relationship with current coach Mike Hesson.
NZC also said on Friday that Buchanan's fellow Australian Kim Littlejohn would not seek re-appointment as the head of the national selection panel.
Littlejohn will stay until September to see out his contract and a panel will be set up to appoint his successor, NZC said.
A review of the selection process has also given Hesson a greater role in picking the team He will have final approval for central contracts and home series, while the coach and captain will select the matchday teams when they are on tour.
"We believe the head coach is best placed to understand the selection challenges and the relative strengths and weaknesses of their squad, as well as having the best knowledge of the conditions and the opposition," NZC chief David White said.
"Ultimately the head coach is accountable for the performance of their team and this selection structure reinforces that."
- Sports & Recreation