People had already noticed changes in the bar, such as how a lot of their pictures had already been taken down, she said.
"It's great to have Rotorua embracing its only Irish bar and having people celebrating."
She said later in the day they were expecting a lot of travellers.
A group of Cantabria Rest Home residents were among those out in green celebrating. Activities co-ordinator Lesley Young said the group were all originally from Ireland, England and Scotland. Volunteer Jenny Cawte said St Patrick's Day was in their background and still meant a lot to them. She said they had come to Hennessy's for lunch, and had really enjoyed dressing up.
Other bars around Rotorua were also expecting a busy night, with some holding competitions and offering special deals to mark the Irish holiday.