It stars Anne Hathaway as Andrea Sachs, a recent college graduate who goes to New York City and gets a job as a co-assistant to powerful and demanding fashion magazine editor Miranda Priestly, played by Meryl steep. Emily Blunt and Stanley Tucci co-star in support of two leads, as catty co-assistant Emily Charlton, and critical yet supportive Art Director Nigel. Andrea “Andy” Sachs (Anne Hathaway) is an aspiring journalist fresh out of North-western Uni. Despite that she knows a little about the fashion industry, she lands the job “A million girls would kill for”: junior personal assistant to Miranda Priestly (Meryl Steep), the icy editor-in-chief of Runway fashion magazine. Despite having little knowledge of fashion, Andy puts up with Miranda’s bizarre and humiliating treatment in hopes of getting a job as a reporter or writer somewhere else. At first, Andy fumbles with her job and fits in poorly with her catty co-workers especially Miranda’s British senior Emily Charlton (Emily Blunt). During a dinner with her father, who came to visit her in New York City, Miranda calls her: the airports, in Florida where she is, are all closed due to a hurricane but she needs to get home and orders Andy to get her home somehow.
Andy tries every airline company there is, but none of them are flying out because of the weather. When Miranda does arrive back at the office she tells Andy she has disappointed her more than any other of her previous assistants. Andy has a talk with Runway’s art director Nigel (Stanley Tucci), who gives a whole new perspective of Miranda, her work and fashion in general. Andy decides to change and, with Nigel’s help, gradually learns her responsibilities and begins to dress more stylishly. Slowly Andy begins to sacrifice her personal life to her career. Miranda notices the change in Andy and gives her a new task: delivering “The Book” (a mock-up of the next edition’s feature spreads) to her Upper East Side townhouse. Andy feels proud as Emily told her before that Miranda doesn’t allow ‘strangers’ in her house. Emily explains to her that she has to behave as if she is ‘invisible’ while she delivers the book at Miranda’s house. However, Andy is tricked by Miranda’s daughters into going upstairs, where she walks in on Miranda and her husband arguing. Mortified, she drops the book and leaves.
Miranda punishes Andy by giving her an impossible task: securing the unpublished manuscript for the next book in the Harry Potter series for her twin daughters to read on the train. Andy is just about to quit when Christian Thompson (Simon Baker), has found the manuscript for Andy. Andy delivers the copy of the manuscript to a stunned Miranda, who still gives Andy a hard time for not having two manuscripts for both of her daughters to read at the same time, but Andy was prepared and already gave the twins two copies, while the one she gave Miranda was just a backup. Andy keeps her job, much to her boyfriend’s disappointment. When Emily falls ill, Miranda commands Andy to accompany the two of them to a charity benefit, where they masquerade as partygoers while actually Emily whispers to Miranda the names of the people approaching her for greeting. At the event, Andy saves Miranda from being embarrassed by Emily, who had forgotten one of the names; meets Jacqueline Follet, the editor-in-chief of French Runway and Miranda’s rival; turns down an offer to meet a big publisher from Christian, but all the while misses her boyfriend’s birthday party.
One evening, while returning The Book, Miranda informs her that she needs “the best team possible” for her Paris trip, which means stepping over Emily. Andy hesitates, as Emily has been boasting about going to Paris for months, but Miranda tells her that declining will send the message that she is not committed to her job or any future job at another publication. Faced with this threat, Andy accepts. The next day Miranda then tells Andy to be the bearer of bad news to Emily who, meanwhile, is hurrying back to the office after purchasing scarves from Hermes of Paris for Miranda. Just as Andy is about to tell her, Emily crosses at a “no cross” point and is hit by a taxi. Andy has a rough day confronting Emily about Paris and then at her friend Lily’s art gallery, where she accepts a kiss on the cheek from Christian.
Lily catches this and berates Andy, to then confront her boyfriend about the fact that she is going to Paris. He realizes that they no longer have anything in common, and they break up. In Paris, Andy attends the shows and even meets designer Valentino Garavani, being introduced as “the new Emily”. One night Andy comes into Miranda’s suite only to find her in her bathrobe, undressed, and crying. While deciding on a seating chart, Miranda opens up saying that her husband is divorcing her, and again the press would write rude things about her such as ‘career obsessed woman’ who doesn’t care for family but that her biggest worry is for her daughters, who have lost yet another father figure. Later, Andy learns from Nigel that he has landed a job as creative director at fashion designer James Holt’s new company. Andy has dinner with Christian who figures out that she is single again. After a few glasses of wine she succumbs to Christian’s charms. In his hotel room the next morning, while dressing, Andy finds out that Runway’s owner is planning to replace Miranda with Jacqueline Follet. Surprised, she asks Christian about it who confirms it saying that Miranda has become old and that Jacqueline will bring fresh change to the magazine.
Andy rushes to the door while Christian stops her calling her ‘baby’ to which she replies that she is not his ‘baby’. Andy storms out to find Miranda and warn her. When Andy finally tells her, Miranda seems unfazed. At a luncheon in honor of James Holt, Miranda announces that Jacqueline will be the new creative director of James Holt’s company much to the surprise of Andy and Nigel. En route to another event, Miranda explains to a still-stunned Andy that she knew about the plan to get rid of her all along, but she found an alternative for Jacqueline and presented “The List” (a list of all the designers, stylists, company owners, and models that were “raised and nurtured” by Miranda and who have promised their loyalty to her whenever and should she ever leave Runway) to the owner of Runway, who realized that without those people, Runway would suffer greatly, and was forced to reconsider. Miranda also says that she was pleased by Andy’s display of loyalty and that she sees a great deal of herself in her.
Andy says she could never do to anyone what Miranda did to Nigel. Miranda replies that she already did, in stepping over Emily. Miranda tentatively comforts her, saying that those choices are necessary to live the life that she lives. At the event, Andy gets out of the car and simply walks away. When receiving a call from Miranda, she throws her phone into a fountain on the Place de la Concorde. Back in New York, she meets her boyfriend for breakfast. He has accepted an offer to work as a sous-chef in a popular Boston restaurant. Andy is disappointed, but her hope is rejuvenated when he says they could work something out. Andy goes to an interview for a newspaper job.
The interviewer reveals that Miranda told him she was by far her biggest disappointment, but that if he did not hire her, he would be an idiot. Afterwards Andy calls Emily while walking past the Runway office and offers to send Emily all of the outfits Andy got while in Paris, Emily feigns imposition saying the clothes will “absolutely drown her” but accepts. After the call Andy then sees Miranda getting into her car across the street. They exchange looks and Andy smiles at her, but Miranda acts as if the two are strangers, which Andy takes in good grace. Once in the car, Miranda smiles slightly before curtly telling her driver, “Go.”.