The 66-year-old Hadlee, who is considered one of the finest fast bowlers of all time having retired in 1990 with 431 test wickets, had surgery after a routine checkup discovered a tumour.
"This operation went extremely well and he has made an excellent recovery from surgery," his wife Dianne said in a statement issued by New Zealand Cricket.
"As a safeguard, further treatment in the form of chemotherapy will commence shortly and last for a few months.
"It is expected that, in time, he will have a full recovery."
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The right-arm fast bowler, who was the first player to take 400 test wickets and held the record for most wickets until India's Kapil Dev surpassed it in 1994, was also a handy all-rounder scoring two test centuries.
(Reporting by Greg Stutchbury; Editing by Toby Davis)
