安妮公主（奥黛丽-赫本饰）代表王室出访欧洲各国，她的最后一站是罗马。面对罗马美丽的风光，安妮颇为心动，很想出去逛逛。可是侍从们却以公主身份特殊不宜抛头露面为由拒绝了她，为了让公主安静下来，他们给她注射了镇静剂，公主在药效发作之前偷偷溜出大使馆

在城市广场上的一个长椅上，安妮公主药效发作，迷迷糊糊地昏睡过去。此时美国驻罗马的记者乔-布莱德里（格里高利-派克饰）正好经过，他以为安妮是个醉酒的少女，担心她发生意外，于是将她带回自己的住处。第二天乔看到报纸上公主的照片，这才得知安妮的身份。为了拿到头条新闻，乔陪安妮开始了罗马一日游，期间发生了不少有趣的事情。两人在短暂的相处中暗生情愫，但碍于身份，这份感情只能深埋在心里。最终乔在媒体招待会上，将公主的照片当成礼物送给安妮。

Princess Anne (Audrey Hepburn) visited European countries on behalf of the royal family, and her last stop was Rome. Facing the beautiful scenery of Rome, Anne was quite moved and wanted to go out for a stroll. But the attendants rejected her on the grounds that the princess was too special to show her face. In order to calm the princess down, they injected her with a sedative, and the princess sneaked out of the embassy before the effect of the medicine took effect

On a bench in the city square, Princess Anne fell asleep in a daze after the drug took effect. At this time, Joe Bradley (Gregory Peck), an American reporter stationed in Rome, happened to pass by. He thought Anne was a drunk girl and worried that she would have an accident, so he took her back to his residence. The next day Joe saw the picture of the princess in the newspaper, and only then did he know Anne's identity. In order to get headlines, Joe and Annie embarked on a day trip to Rome, during which many interesting things happened. The two had a secret love during their short time together, but due to their identities, this feeling can only be buried deep in their hearts. In the end, Joe gave Anne a photo of the princess as a gift at the media conference.