Fiesta: The Sun Also Rises is the story of a group of young men from America and Britain, who travel to Spain in order to witness the Festival of San Fermin in Pamplona. There, they witness bullfights and bulls running. The chief protagonist of the story is Jake Barnes, who is a journalist with war wounds. In Spain, he falls madly in love with a twice-divorced woman, Lady Brett Ashley.

The book is written in three parts. The first part describes the budding love story of Jake Barnes and Brett. Despite her promiscuous credentials, Jake finds Brett irresistible and falls for her. Brett confesses her love for Jake but both seem to know that a stable relationship may never be on the cards. The story moves on to part two with more characters coming in and falling in love with Brett. Jake is joined by Bill Gorton, Robert Cohn, a young matador named Romero and Brett's fiancé Mike Campbell. Cohn begins to desist everyone else in the group because of their anti-Semitic remarks about him but the group continues to hold up. The tensions continue to mount as each of them has their moments with Brett. The tensions eventually erupt in a fistfight. In the final part of the book, each of the characters are reminiscing about their past and what might have been in the aftermath of the fistfight.