It was their first stop on a nine-day tour of the Far East and South Pacific in celebration of the queen's Diamond Jubilee.
The Duke and Duchess of Cambridge were welcomed by an honor guard as they met Singapore's president. Kate wore a pale floral dress to the event. She was carrying an orchid bouquet when she and William greeted staff and spectators at the historic Raffles Hotel later in the day.
Diana was due to visit the white orchid named in her honor in 1997, but was killed in a car crash two weeks earlier.
The couple is also scheduled to visit the Solomon Islands and Tuvalu.
The Associated Press contributed to this report.