Akeem and Lisa end up getting married, with Lisa being lovingly accepted as the new Princess of Zamunda.
Akeem (Eddie Murphy - who also plays multiple characters) is a fabulously wealthy Prince of the fictional African nation Zamunda. All his needs are met and his parents King Jaffe Joffer (James Earl Jones) and Queen Aoleon (Madge Sinclair) have even hired a girl to be raised from childhood solely to serve as Akeem's wife. Akeem, however, has grown tired of his royal life where nobody stimulates him intellectually (his betrothed has no opinions on anything, only saying that her favorites are the same as Akeem's). Akeem convinces his father to let he and his faithful servant Semmi (Arsenio Hall - who also plays mulriple characters) visit New York City to "sow his royal oats" when, in fact, Akeem plans to find an American girl to be his bride.
Semmi clearly enjoys the high-life and is distressed when Akeem forces them to move into a slum in Queens and live life as poor immigrants. Akeem and Semmi get a job at a fast-food restaurant named "McDowell's," which is owned by a sleazy, wealth-crazed businessman named Cleo McDowell (John Amos) who is clearly ripping of the McDonald's model. When Akeem meets Cleo's eldest daughter Lisa (Shari Headley), he is immediately smitten with her intelligence and passion. Unfortunately, Lisa is dating a wimpy but wealthy man named Darryl Jenks (Eriq LaSalle) whom Cleo loves due to his wealth.
Akeem gets nowhere with Lisa until she watches he and Semmi defend the store from a thug who tries to rob it (cameo by Samuel L. Jackson). Initially, Lisa tries to set Akeem up with her younger sister Patrice (Allison Dean), but Akeem is persistent in his pursuit of Lisa. Cleo does everything he can to keep Lisa with Darryl, not wanting her to marry such a poor man. Despite Cleo's best efforts, Lisa eventually falls for Akeem. Meanwhile, Semmi becomes fed up with the impoverished lifestyle and spends all their money, causing him to send a telegram to Jaffe asking for more money. This causes Jaffe and Aoleon to travel to America to see what has happened to the pair.
When Jaffe arrives, he can't find Akeem (who is trying to avoid him as he has not yet succeeded in getting Lisa to agree to marry him, nor has he told her that he is a fabulously wealthy prince). Semmi takes the royal parents to Cleo, who gets excited to learn that Akeem is fabulously wealthy and kicks Darryl out of his house (although it later appears that Darryl hooks up with Patrice). After Cleo finds Lisa, Jaffe tells her that Akeem has been playing her as he has a bride waiting in Zamunda and, anyways, Zamundan law would not allow Akeem to marry a foreigner. Lisa runs off in tears while Cleo yells at Jaffe for insulting his daughter.
Jaffe finally finds Akeem, who is distraught upon learning of his father's actions. Akeem then runs off to find Lisa. Aoleon is also mad at Jaffe, reminding him that as king, he could change the law to allow Lisa and Akeem to marry. Akeem tracks down Lisa and tells her the truth about who he is, confessing his genuine love for her and even offering to abdicate his throne to stay with her. She tearfully refuses and Akeem and Semmi return home with Akeem's parents.
We jump ahead to Akeem's wedding day as he dourly watches his betrothed walk down the aisle. When he lifts the veil, he is surprised to find Lisa underneath. She has changed her mind and Jaffe has changed the law. The two happily marry as all their parents watch on. As they drive away, Semmi is caught flirting with Akeem's initial "fiancee." Akeem offers again to abdicate the throne, but Lisa turns him down, thrilled at being his Princess.
There is also a cameo of the characters the Duke Brothers from another Eddie Murphy film - Trading Places.