At the hearing, nearby residents raised their concerns about a number of issues including the impact the subdivision would have on the volume of traffic using steep and narrow roads on the hill.
Submitters also raised concerns about the visual impact of the towers and what was seen as a lack of recognition being paid to the historic and cultural significance of the site.
In his decision, Mr Garland said developments on such sites "present a particular challenge" in terms of weighing up efficient use of the property while at the same time minimising adverse effects.
A particular factor was Napier's district plan specified that the "existing build form" of the long-closed hospital "provides a relevant context" for assessing consent applications lodged before next year.
"On balance, I have concluded that the purpose of the [Resource Management] Act will be met by the granting and subsequent exercise of the resource consent," Mr Garland's said in his decision.
"The project appropriately avoids, remedies and/or mitigates potential adverse environmental effects if it is carried out within conditions which have been agreed with council officers."
Those conditions include a requirement to make improvements to neighbouring Hospital Tce and to complete other roading developments around the site.
Todd Property Group managing director Evan Davies was unable to say yesterday when work would begin, or when the subdivision was expected to be completed.
However, he said the company was pleased to have received approval for the final stages of what would become a new residential community.
"We appreciate the support that we are receiving from the local community as we transform the neglected former hospital site into a fantastic new living environment. We are looking forward to the next phase of this unique and exciting project," Mr Davies said.
Each of the development's two 28.5m-tall high-rise blocks will have 18 apartments. One will house a ground-floor public cafe and the other will have a gym for apartment residents.
Napier City Council senior planner Paul O'Shaughnessy said under the Resource Management Act, the developer and those who had made submissions had until the end of January to lodge any appeals against the decision.