Data released under the Official Information Act shows Invercargill Prison and Otago Corrections Facility registered two suspected suicides in the past year, one in each facility.
Before that, neither facility had registered any suspected suicides since at least 2016.
It comes amid an increase in numbers of suspected suicides across the country.
Corrections recorded eight suspected suicides in 2019-20 across the country but in 2020-21 this number increased to 10.
Department of Corrections deputy chief executive Juanita Ryan acknowledged the increase and said the department was continuing to invest in intervention and support measures.
Research carried out by Corrections showed 62% of those in prison would have met the diagnostic criteria for either a mental health or substance abuse disorder within the last 12 months.
The research also said 91% would have met those diagnostic criteria at some time during their lives.
Ms Ryan said the Corrections role had expanded to strengthen response and support the needs of this group in light of the escalation of mental health issues for people in prison.
"We make every effort to ensure people’s mental wellbeing and physical safety during their time in custody," he said.
"This can be extremely challenging for our frontline staff, who do an incredible job working with some very complex people."
She said Corrections was taking a proactive approach to ensure people in prison received the support they needed.
Staff had the training and resources to keep everyone safe, she said.
Ms Ryan highlighted that Corrections had restructured its health services last year, which gave regional nursing and mental health leaders the tools for a strong regional approach.
"It supports more agile ways of working and collaboration between national office, regional nursing and medical officer services and mental health teams."
Other changes included establishing specialist heads of profession, with a strong focus on delivering a model of care that best met the needs of Maori as an overrepresented group in the prisons, she said.
"Corrections is committed to preventing unnatural deaths and life-threatening incidents of self-harm in prisons.
"The causes of suicide are complex and people in prison are a known high-risk group.
"Corrections is doing more than ever in the area of supporting people’s mental health issues."
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