Jenkin said the carpark, a building opposite the hospital's Emergency Department, is lit but that the incidents took place in daylight, within an hour of each other.
DHB security and the police were notified soon after, she said.
Jenkin said security patrol the area and the DHB had increased its security presence on campus.
"We have also notified our staff on the intranet and advised them of the incidents and to be extra careful when walking to their cars to or from shifts.
"They can contact security if they want escorting to their car or we advise them to walk with a colleague."
Hamilton police are calling for witnesses to the two indecent assaults and say they are looking for one offender, a teenager who struck twice yesterday afternoon.
The offender is described as Pākehā, aged about 16, and 1.83m [6 foot] tall.
He was wearing a black baseball cap, light-coloured long-sleeved T-shirt, green pants and black gumboots.
Acting Detective Sergeant Harry Hodgson said police were actively working to find the person responsible for the two assaults.
"While we have been working with the hospital and have reviewed CCTV footage, we are also asking the public for their assistance.
"We would like to hear from anyone in the vicinity of Waikato Hospital yesterday between 4pm-6.30pm or anyone who may have information on who this young man is."
Information can be provided to Hamilton police on (07) 858 6200 or to Crimestoppers anonymously on 0800 555 111.
