The story takes place in London in 1910, Mr. Banks (David Tomlinson) is a bank clerk, and Mrs. Banks (Glynis Johns) is obsessed with women's rights movement. The two, who are busy with official duties, have no time to take care of their children, Mike (Matthew Garber) and Jenny (Karen Dotrice). They can only ask a nanny to do it. However, what the couple don't know is that the weird brother and sister are not something that ordinary nannies can handle! A beautiful girl named Mary (Julie Andrews) comes to the Banks family to apply for a nanny position. She left a deep impression on Mike and Jenny as soon as she appeared. It turned out that Mary was a fairy. Her arrival made the two children feel family and friendship again, and also made Mr. and Mrs. Banks understand what the ultimate thing in life is.