Alex and Rosie have been best friends for almost as long as they can remember. During Rosie's 18th birthday party, Alex kisses Rosie, who is drunk, and realizes that he has romantic feelings for her. The next day, while nursing a hangover and having had her stomach pumped, Rosie regrets having got drunk, and tells Alex that she wishes that the night had never happened. Alex interprets her words as Rosie just wanting to be friends. Greg, the "fittest guy in their year", asks Rosie to the school dance. While she originally intended to go with Alex, she accepts Greg's offer when she learns that Alex is thinking about going to the dance with a girl named Bethany. After the dance, Rosie has sex with Greg, but the condom slips off inside her. Rosie aspires to one day run her own hotel, and applies and gets accepted to a hotel management course at Boston University. She rushes to tell Alex but finds him having sex with Bethany, which causes her to vomit. Rosie discovers that she is pregnant but refuses to tell Alex, fearing that he will forgo his chance to study at Harvard to help take care of her. After Alex leaves for the United States, she gives birth to a daughter, whom she names Katie. Alex learns of Rosie's pregnancy from Bethany and becomes Katie's godfather. Five years later, Rosie visits Alex in Boston and they spend a night together talking and visiting places. The following morning, she discovers that his girlfriend is pregnant. She understands that Alex's living situation was not proper and tries to discuss it with him but he rebuffs her, saying that at least their child will have both parents. Infuriated, Rosie leaves Boston immediately. She reconciles with Greg, who had initially fled to Ibiza upon learning of her pregnancy, and the two eventually marry. Later, Rosie learns that Alex split from his girlfriend after discovering that the baby was not his. She bumps into Bethany, now a famous model, and suggests that Bethany look up Alex on an upcoming trip to the US. Rosie's father dies. Alex attends the funeral, where he reconciles with Rosie. At the same event, Greg behaves immaturely, causing a scene. This later prompts Alex to write Rosie a note saying that she deserves better and that he can be that better man. However, Greg intercepts the note and hides it from Rosie. Later, Rosie discovers that Greg is cheating on her and kicks him out. While disposing of his things, she finds the letter from Alex. She calls him, but discovers that Bethany is living with him now and that the two are engaged. They invite Rosie to be the "best man" at their wedding. Rosie plots to interrupt the wedding, but fails, as the church ceremony is over by the time she arrives. At the reception, Rosie gives a speech, telling Alex that she loves him as a friend. Her daughter, Katie, brings a friend named Toby with her to the wedding, in a friendship that is reminiscent of Rosie and Alex when they were children. During a dance, Toby suddenly kisses Katie, but Katie pushes him away and runs outside. Rosie and Alex follow her. Alex counsels her and tells her to follow her feelings with Toby or she might regret it, alluding to how he felt about Rosie. After a moment, Toby finds Katie and apologizes for what he did. As he asks her to forget what just happened, Katie interrupts him with a kiss. In that moment, Alex learns that Rosie does not remember the kiss that they shared on her 18th birthday. He realizes that he had been mistaken in interpreting her desire to forget that night as her wanting to stay platonic. Years later, Rosie finally fulfills her ambition to start her own hotel. Alex is her second guest. When he arrives, he tells Rosie that he ended his marriage with Bethany, and shares with her a recurring dream he has had about the two of them being together. Finally, they kiss.
Love, Rosie received negative reviews from critics. On Rotten Tomatoes, the film has an approval rating of 33% based on reviews from 55 critics, with an average rating of 4.6/10. The site's consensus states: "Lilly Collins and Sam Claflin are appealing, and they give it their all, but they're undone by Love, Rosies silly, clichéd storyline." On Metacritic, the film has a score of 44 out of 100 based on reviews from 16 critics. Donald Clarke of The Irish Times described Collins as "perfectly charming", but felt that "entire film is weighed down by such sloppy storytelling and by equally disordered characterisation" and gave the film one out of five stars calling it awful, but pretty.
