Seventy-year-old widower Ben Whittaker, a retired executive from DEX One, applies to a senior citizen intern program after retirement has become too boring for him. The company in Brooklyn he applies to is About the Fit, a fast-growing e-commerce fashion startup, whose founder and CEO Jules Ostin had previously agreed to a community outreach program where seniors would intern at the firm. Ben impresses everyone and is one of four hired.
Ben is assigned to work with Jules, who is somewhat skeptical at first. Initially frozen out by her, Ben slowly wins over co-workers with his congeniality and gets into Jules's good graces. Ben heads to work one day extra early to organize a desk that Jules had complained about the messiness of previously. After work, Ben notices Jules's chauffeur drinking, convinces the driver to leave and drives Jules home himself, a role he retains in days to come.
Ben eventually reveals that he once worked in the very same building where About The Fit is now based. He develops a romantic relationship with the in-house massage therapist, Fiona, and becomes something of a father figure to the younger workers, such as offering one intern advice for what to wear when making a delivery to Beyoncé and Jay-Z and providing another with a place to stay at his house after the other man is evicted by his parents. Ben is very committed to Jules, and even breaks into the house of Jules's mother to delete an embarrassingly scathing email that Jules inadvertently sent her, narrowly avoiding getting arrested in the process. Ben also gets to know Jules' family. Her husband, Matt, gave up his own career to be a stay-at-home dad to their daughter, Paige (JoJo Kushner), when About The Fit started to take off. However, their marriage is slowly breaking apart over Jules's long hours, mainly caused by her very hands-on management style.
Meanwhile, Jules is under pressure to give up her post of CEO to someone outside of the company as her investors feel that she is unable to cope with the workload, having grown About The Fit from a startup founded in her kitchen to a 220-employee juggernaut in only eighteen months. Believing it will give her more time at home with her family, Jules is willing to consider the offer. While driving Paige home from a party, Ben discovers that Matt is having an affair with another parent at Paige's school. While on a business trip in San Francisco to interview a potential CEO candidate, Jules reveals that she knows about Matt's cheating as well, but didn't confront Matt about it because she blamed herself for not spending enough time with him.
In an effort to buy herself the time to repair her marriage, Jules decides to hire a prospective CEO. When Jules goes to Ben's home the next day, Ben greatly encourages Jules to think about how much this will change her authority and how her creativity may be tampered with and also reminds her of her passion for her company. Matt unexpectedly drops in at the office and urges her to reconsider, saying that he is willing to make their marriage work. Jules goes out looking for Ben, wanting to tell him that she has changed her mind and finds him enjoying his Tai Chi exercise group. She finally lets herself relax and joins him.
Originally set up at Paramount Pictures, The Intern was planned to feature Tina Fey and Michael Caine in the lead roles. When a budget could not be settled, Meyers decided to pre-package before going out to other studios and was able to start negotiations for both actors. Handed over to Warner Bros., Fey was replaced by Reese Witherspoon as the attached star, though Witherspoon left the film on January 15, 2014, due to scheduling conflicts. On February 7, 2014, Anne Hathaway was in final talks to replace Witherspoon in the lead role. Stephen Goldblatt was set as director of photography. On June 23, 2014, Zack Pearlman joined the cast of the film.
Principal photography began on June 23, 2014, in Brooklyn, New York City, where De Niro was spotted on the set of the film. Filming was completed on September 29, 2014.
The first trailer was released on May 13, 2015, and was later attached to showings of Me and Earl and the Dying Girl, Pitch Perfect 2, and Paper Towns. On August 3, 2015, another trailer was released.
The Intern grossed $75.7 million in North America and $118.8 million in other territories for a worldwide total of $194.6 million, against a net production budget of $35 million.
In its opening weekend, the film opened alongside Hotel Transylvania 2 and was projected to gross $15–20 million in its opening weekend. It ended up grossing $17.7 million, finishing second at the box office behind Hotel Transylvania 2 ($48.5 million).
On Rotten Tomatoes, the film has an approval rating of 60% based on 174 reviews, with an average rating of 5.8/10. The site's critical consensus reads, "The Intern doesn't do enough with its timely premise, but benefits from the unorthodox chemistry of its talented leads." On Metacritic, the film has a score of 51 out of 100, based on 36 critics, indicating "mixed or average reviews". Audiences polled by CinemaScore gave the film an average grade of "A–" on an A+ to F scale.
Richard Roeper of The Chicago Sun-Times gave the film an "A–", stating, "With some genuinely insightful dialogue, a number of truly funny bits of physical business, and small scenes allowing us to get know and like a half-dozen supporting players, The Intern grows on us from scene to scene, from moment to moment."
Manohla Dargis of The New York Times wrote that the film was similar to Meyers's other works, stating that it was "frothy, playful, homogeneous, routinely maddening and generally pretty irresistible." Despite criticizing Meyers's screenplay and "conflicted ideas about powerful women," Dargis praised the casting of De Niro, stating he "owns the movie from the moment he opens his mouth." Hathaway's role was derided as "less of a character and more of a fast-walking, speed-talking collection of gender grievances."
Director Quentin Tarantino viewed the film as Oscar-worthy, stating “It does seem to be to some degree there’s a boom or bust aspect when it comes to Hollywood when it comes to female directors. There becomes an era when there’s a lot working then that settles down and there’s a dry period—but frankly, maybe I’m just talking shit because the thing is there are female directors. Maybe they’re not being the ones that are being asked to be on The Hollywood Reporter roundtable. One of my favorite movies this last year was Nancy Meyers’ The Intern. They’re not considering that for the Oscars even though I think Robert De Niro gave one of the best performances this year in that movie. I thought the script was actually one of her best. Right up there with It's Complicated. They’re not asking her to be part of the discussion.” Similarly, Clem Bastow, writing for The Guardian, suggested that poor reviews for the film were primarily coming from men, who form the overwhelming majority of film critics.
The film was well-received by audiences, receiving a rating of 74% on Rotten Tomatoes, 6.7 on Metacritic, 7.2 on IMDb, and an average grade of "A-" on an A+ to F scale from CinemaScore.