Let's Make It Legal begins at the end--the end of the long marriage between beautiful grandmother Miriam (Claudette Colbert) and her chronic-gambler husband Hugh (Macdonald Carey). Barbara (Barbara Bates), the daughter of the couple, hopes to bring her parents back together, which proves to be a difficult proposition when Miriam's old flame Victor (Zachary Scott), now a millionaire, arrives in town. Hugh tries all sorts of comic strategies to win his ex-wife back, but to no avail. Ultimately, Miriam must choose between the financially solvent Victor and the impishly irresponsible Hugh. This being a comedy, it isn't hard to figure who's going to be headed to the altar at fade-out time. Let's Make It Legal was partly designed to showcase two of Fox's up-and-coming contract players: Robert Wagner and Marilyn Monroe.
~ Hal Erickson, All Movie Guide