Tillie Jones, a fetching student at the Modern Secretarial School, wins the heart of Clarence MacDougall, a bookkeeper for the Simpkins Dress Company, when she accidentally rams his car outside the office building in which he works and she attends school. Consequently, when Mac's boss, Mr. Simpkins, fires his secretary, Mac suggests hiring Tillie. At the office, Mac soon discovers that he must vie for Tillie's affections with Wally Whipple, the office manager. Finding her shorthand deficient, Tillie writes a letter from memory that Simpkins has dictated to George Winker, a potential partner. When Tillie transcribes Simpkins' negative comments about Winker into the document, Winker threatens to sue for slander and dissolves their partnership negotiations. Before leaving the office, he also steals the next season's fashion designs. Simpkins is about to fire Tillie when his attorney calls to warn him that Winker is a crook. Relieved that Tillie's faux pas prevented him from entering into business with Winker, Simpkins goes to Chicago on business and puts Mac is charge of the office, instructing him to send the new Benton line of dresses into the workroom as soon as they arrive. When Ted Williams, a dress designer who has been trying to sell his designs to Simpkins, appears at the office, Tillie mistakes him for the Benton representative and sends his sketches into the workroom. Deciding that Simpkins should display his dresses in a prestigious fashion show being staged at a local hotel, Tillie convinces Mac to underwrite the expenses for the show and appoint her head model. On the day of the pageant, Simpkins returns to the office and finds an army of bill collectors demanding payment for their services in staging the show. Furious, Simpkins hurries to the hotel, where he encounters Winker who brags that he is exhibiting the Benton styles. Determined to best Winker, Simpkins allows Tillie's show to continue, and when it is over, his fashions win all the laurels and an avalanche of orders. Thrilled, Simpkins promotes Mac to general manager and puts Tillie in charge of style promotion. Whipple is then forced to bid Tillie and the business farewell when he is drafted into the Army.