Casting
Roger Mussenden was hired as casting director, and he held casting calls throughout the United States including San Antonio, Texas, Miami, Chicago, New York City, and Los Angeles. Casting calls began on March 16, 1996, and concluded on March 23. Over 21,000 people auditioned for the title role, becoming the second largest audition since the search for Scarlett O'Hara in Gone with the Wind (1939). Casting turnouts reached 10,000 in Los Angeles and 5,000 in Chicago, while turnouts reached 8,000 in San Antonio. Mussenden chose newcomer 10-year-old Rebecca Lee Meza of Harlingen, Texas to portray young Selena.
Mexican actress Salma Hayek was invited to test the role of Selena by Esparza. Hayek turned the role down; she said she felt it was "too early" to base a movie on Selena and that it would be too emotional. Abraham discovered an actress in Los Angeles and wanted her for the role as Selena, despite her inability to convince the casting crew. He later had a change of heart when American actress and dancer Jennifer Lopez showed up for the audition.
Lopez found the audition process an elaborated procedure and was asked to sing, dance, and act out the elopement scene in front of the casting crew and Abraham. Within three takes of the elopement scene, Lopez convinced the entire casting crew who believed her performance was "among the strongest". Lopez had previously worked with Nava in My Family (1995). Screen testing was described as "grueling" and required "nine minutes of singing and dancing and eight pages of script." After the announcement that Lopez would portray Selena, news media and fans criticized Abraham for choosing Lopez, a New York City native born to Puerto Rican parents, to play a Texan of Mexican descent.
The Mexican media disapproved of the film and were outraged that Lopez was chosen for the title role. Lopez received backlash from the media and fans because she was not a Mexican American. The Hispanic community began protesting for a recast. During pre-production, Lopez stated: "I know a few people were protesting, but in Corpus [Selena's hometown] everyone has been really supportive". Nava admitted that the backlash was "a little hurtful", and felt the protesters "should be celebrating that we have an all-Latino cast and that Lopez, one of our own, is becoming a star." The announcement was described as the "role of a lifetime," with Lopez's salary for the film reportedly $1M USD, making Lopez the highest paid Hispanic actress up to that time. Dave Karger of Entertainment Weekly noted that "nothing could have prepared [Lopez] for the hype attached to her million-dollar salary."
On August 8, the Los Angeles Daily News announced that Jon Seda (who is of Puerto Rican descent) and Edward James Olmos (who is of Mexican descent, and previously became as one of the candidates for replacing Nava as the director) had joined the cast as Chris Pérez and Abraham Quintanilla, respectively. After Lopez landed the role, she decided to stay with Suzette Quintanilla, Selena's sister, at her home to study her character in the recordings and footage the family shared with her. Lopez felt that her "spirit and [Selena's] spirit were so similar" which was echoed by the singer's family who found that Lopez mimicked the personality traits of Selena. They believed that Lopez' body language, laugh and how she talked were identical to that of Selena.
Lopez had constant dance rehearsals for the film and said how she would arrive at the studio late in the day after finishing filming for another role. The family often had the entire main cast of the film over for dinner and would notice how they would watch them in their interactions with each other and the way they ate. Edward James Olmos, who took the role as Abraham, was asked to gain 40 pounds (18 kg) for the film. The cast found Olmos to be a father figure for them who often gave advice to the cast during filming.
A.B. found Olmos' portrayal of his father to be convincing, especially in the scene where Abraham was angered after finding out about Selena and Perez' relationship. Band member Pete Astudillo, commenting on production, said he had to do a screen test to play himself and had to improvise in several of his scenes, since he had little dialogue in the film.
Jon Seda often spent time with his subject Chris Pérez for character development. Seda visited Perez at the home he shared with Selena and found a price sticker in the bathroom with a scribbled letter that read "Selena and Chris, I Love You" which further inspired Seda to "show the love they [once] had" in the film. The biographical film focused on Selena's life rather than her death, with Nava saying, "I don't want to attend to [her murder]."
