Born Sidney Arnold Franklin, he was involved in amateur film-making while still at school. With his brother Chester, he wrote, directed and edited a short film The Baby (1915), at a cost of $400. It stirred the interest of D.W. Griffith, who decided to put the brothers to work making children's films for the Triangle Film Corporation. After three years, they went their separate ways. Sidney ended up with the more successful career. He established his reputation with Smilin' Through (1922), and went on to direct some of the great female stars of the silent era, including Norma Talmadge, Mary Pickford and Greta Garbo. He joined MGM in 1926 and remained affiliated with the studio until his departure in 1958.
A protégé of the similarly-inclined chief of production at MGM,Irving Thalberg, Franklin was thought of as a 'literate' filmmaker. He was at his best, bringing classics to the screen, like the Noel Coward adaptation of Private Lives (1931); Reunion in Vienna (1933), based on a play by Robert E. Sherwood; Rudolph Besier's period melodrama The Barretts of Wimpole Street (1934) or Pearl S. Buck's tale of struggling Chinese farmers, The Good Earth (1937). All of them lavishly produced as A-grade features, with A-grade budgets.
From 1939, Sidney spent most of his time as producer on similarly prestigious output, with a strong leaning towards sentimental melodrama. The biggest box office hits were Waterloo Bridge (1940), Random Harvest (1942), Madame Curie (1943),The White Cliffs of Dover (1944), and - a picture he thought would lose money, but needed to be made - Mrs. Miniver (1942). 'Miniver' turned out to be the most popular picture of its year and contributed in no small way to Sidney winning the Irving Thalberg Memorial Award in 1943, for "consistent high quality of production and achievement".