Porter mainly wrote children's literature, including three Miss Billy books (Miss Billy, Miss Billy's Decision, and Miss Billy Married), Just David (1916), Six Star Ranch (1916), Cross Currents (1928), and The Turn of the Tide (1908).

Her most famous novel is Pollyanna (1913), later followed by a sequel, Pollyanna Grows Up (1915).Her adult novels include The Turn of the Tide (1908), The Road to Understanding (1916), Oh Money! Money! (1917), Dawn (1918), Keith's Dark Tower (1919), Mary Marie (1920), The Story of Marco (1920), and Sister Sue (1921); her short stories include "Money, Love and Kate" (1924).Porter achieved considerable commercial success: in 1913, Pollyanna ranked eighth among bestselling novels in the United States, second in 1914, and fourth in 1915 (it went through forty-seven printings between 1915 and 1920); in 1916, Just David ranked third; in 1917, The Road to Understanding ranked fourth; in 1918, Oh Money! Money! ranked fifth.