The daughter of engineer Luiz Eduardo Osório Negrini, and pedagogue Neusa Vidal de Negreiros, who is descended from André Vidal de Negreiros, Alessandra, who has Portuguese and Italian ancestry, has a brother named Paulo Roberto, spent his childhood and adolescence in Santos. At 18 she enrolled in a theater course, and at that time, was called to do tests on Rede Globo.
Her TV debut was in the telenovela Olho no Olho, Antônio Calmon. In 1995, she made great success in the miniseries starring Engraçadinha... Seus Amores e Seus Pecados, based on the work of Nelson Rodrigues.
In 2000, gave birth to Isabel Olinto of the critically acclaimed miniseries A Muralha, a tribute to 500 years in Brazil. Because of the sensual appeal of her character in the miniseries, graced the cover of the Brazilian edition of Playboy magazine in April of that year. The fact that she played a prostitute in the pages of the magazine, the actress made the situation worse in the court responded that the process for taking her son Antônio, then three years old, watching a movie inappropriate for the age, Sleepy Hollow head in a movie Leblon, on February 3, 2000.
In 2002, reaped many accolades for Selma villain of the novel Desejos de Mulher, Euclydes Marinho. In 2003, made an appearance on the soap opera Celebridade, Gilberto Braga, and children's series Sítio do Picapau Amarelo. In the theater, attended parts of Os Credores and A Gaivota, in which he traveled to Europe, Canada and Japan.
In 2007, she starred in the soap opera Paraíso Tropical, Gilberto Braga. In the plot, the actress played the twin sisters Paula and Taís, having been very successful. The same year she premiered the film Cleópatra, Júlio Bressane, for which she won the best actress award at the Festival de Brasília. In 2008, he appeared in two more films: A Erva do Rato, of Júlio Bressane and No Retrovisor of Mauro Mendonça Filho.
Negrini, who was away from novels since 2007, when he made the twins Paula and Taís in the novel Paraíso Tropical, returns to television in 2010 to participate in the series S.O.S. Emergência and As Cariocas.
In 2011, Negrini returns to the stage alongside Karin Rodrigues, to stage the play A Senhora de Dubuque, a text by Edward Albee. And was in the movie O Abismo Prateado and TokyoShow.
In 2012, participated in the new version of the play A Propósito de Senhorita Júlia, the story takes place in Brazil at the beginning of the 21st century. In the same year the novels returns in the second phase of Lado a Lado, playing opera singer Catarina Ribeiro. In 2014, Alessandra plays Susana in Boogie Oogie, novel Rui Vilhena, replacing Meu Pedacinho de Chão.
Negrini was married to actor Murilo Benício from 1998 to 1999. They have one son, Antônio. She was also married to singer Otto from 2001 to 2008, with whom she has one daughter, Betina (born 2003).