Mr Barker was appointed this month and chaired his first meeting of the new board last Friday.
"From now on I want you to consider very carefully whether you can justify putting a board item into the closed agenda," Mr Barker told members and executive DHB staff.
Some things had to be discussed behind closed doors, including commercial negotiations and anything involving patient privacy, he said.
"But those exceptions should be used stringently and carefully."
Last month, the DHB heard eight items in closed session, including an update on the new Buller Health Centre.
Greymouth Star journalists have noted up to 13 in the closed agenda.
Speaking after the meeting, Mr Barker would not say if he thought the DHB had previously been too secretive.
"I'm not making judgements about the past, I'm setting the tone for the future," he said.
The former union organiser, Labour MP and cabinet minister said he felt an affinity for the health sector and for the Coast, although his home was now in Hawke's Bay.
