Marcia Mae Jones received fan mail from disabled children all over the world after playing Klara in this movie.
Marcia Mae Jones was four years older and eighteen inches taller than Shirley Temple when this movie was filmed. Jones later recalled of the scene in which Temple helps her crippled character to walk that if she had really leaned on Temple, she "would have crushed her."
Shirley Temple developed throat problems after she accidentally swallowed fake snow during a winter scene, and the crew had to shoot around her for two days.
Shirley Temple suggested the idea and placement of the "In Our Little Wooden Shoes" sequence because she felt the song would liven up the movie.
Delmar Watson was not allowed to study his lines in advance. Because director Allan Dwan wanted Peter to seem slow, Watson was not given his lines until the day before they were filmed.
A scene in which Heidi teaches Peter to read was cut from the final film.
As she had worried about Jane Withers in Bright Eyes three years before, Shirley Temple's mother, Gertrude Temple, worried that Marcia Mae Jones would steal the spotlight from her daughter in this movie. However, Shirley and Marcia Mae worked well with each other and appeared together again in The Little Princess.
For the scene in which Heidi is butted by a goat and falls over, Shirley Temple was butted for the first few takes. Although she later said that being butted was not painful, her mother Gertrude Temple became concerned for her safety and insisted that a stunt double be used.
Having acted with him four years before in To the Last Man, Shirley Temple chose Delmar Watson to play Peter in this movie.
The movie was filmed during the summer, and Jean Hersholt's heavy costume once caused him to collapse from heat exhaustion.
The scene in which Heidi is suddenly squirted in the face while milking a goat was planned without Shirley Temple's knowledge. A tube of milk was attached to the goat udder where Temple couldn't see it, and when she was squirted, her surprised reaction was genuine.
The scene in which Heidi smuggles a litter of kittens into the house, and the following scene in which Sebastian hides the kittens from Heidi's cat-hating aunt, were in the original book; the scene with the capuchin monkey was written for the film.