The All Black captain edged out politicians, including Prime Minister John Key, in a survey by Oral-B Powerbrush toothbrush company.
McCaw took out top smile honours, winning 43 percent of the vote.
Mr Key's grin came in at 38 percent - equal with Sir Peter Jackson. The smile of former Prime Minister Helen Clark and the upside-down smile of World Cup coach Sir Graham Henry received 5 percent of the vote.
The survey also found one in 10 New Zealanders brushed their teeth less than once a day and more than half had early signs of gum disease.
Just 55 percent of Kiwis brushed their teeth the dentist-recommended twice daily, the survey found.
The study showed 81 percent of the population had cavities, and 51 percent experienced bleeding gums, a common sign of gingivitis.
The inflammatory gum disease is due to the long-term effects of plaque deposits.
Only 18 percent of New Zealanders floss daily, 15 percent using mouthwash every day.
Dr Hisham Abdalla, an Auckland-based international lecturer in dentistry, said aside from bad breath the financial and social costs of oral disease were a serious burden on society.
"Poor oral health can lead to gum disease which can seriously affect general health,'' Dr Abdalla said.
"[It] can progress to destroying the jawbone over time, leading to tooth loss. Gum disease over a period of time increases the person's risk for many other diseases.''
Cost was nominated as the main reason for not visiting the dentist by 84 percent of people, followed by pain at 13 percent and inconvenience at 9 percent of respondents.
The online survey of 1000 people was carried out by the firm Perceptive.
