Canterbury DHB says 77 patients suffered serious harm while being treated in just one year.
The DHB has released its serious adverse events report for the year between July 2018 and June 2019.
It says a serious adverse event is one where a patient needs significant additional treatment, or has died or been seriously injured.
Most patients who suffered harm in their care either had a fall or developed a bedsore.
47 of these incidents were falls which resulted in fractures or head injuries, while 14 patients had developed bedsores.
Included in the report were deaths of two babies, one because incorrect information was entered on a patient board.
One patient also suffered a heart attack after a tube was put into the wrong part of his body.
CDHB says it's working on key initiatives to reduce such events.