Mr Key lived in Singapore for a year during the mid-90s when he headed investment bank Merrill Lynch's global foreign exchange division, and his speech was pitched as if the audience included former clients.
He pointed out Singaporean interests have considerable holdings in New Zealand hotels and other property, although the Herald understands new investment has slowed in recent years.
Mr Key noted much of the existing investment was in Christchurch, including some well-known hotels.
The fact the Millennium Hotel was being rebuilt after suffering damage in the quake was a sign of confidence in Christchurch's future, he said, looking for the hotel's Singaporean owner in the audience.
The series of earthquakes, said Mr Key, were "not an event we are likely to see again in anyone's lifetime. We would certainly encourage you not to be deterred in terms of your investments in New Zealand."
Talking about his Government's economic management, Mr Key said the primary focus was to get New Zealand's books back into surplus and to make the economy more productive.
"We went through a period, in the 2000s if you like, where New Zealand lost competitiveness."
Policies of that period saw the economy stand still and they didn't serve the country well. But Mr Key said he and his Government were "positive about what's happening in New Zealand and about our outlook".