Starring as the Villan of new prime-time telenovela this year, Mariana has proven that her mix of an Argentine mother and a Cuban-Mexican father, is a great combination for success. Seoane demonstrated an interest in becoming an entertainer since a very early age. She began acting and singing professionally as a teenager. It is the former career, however, that has brought her much fame in Mexico and Latin America.
In 1995, Seoane made her acting debut on a Televisa telenovela, when she appeared on Retrato de Familia ("Family Photo"), alongside Alfredo Adame, Helena Rojo and Julio Bracho. Seoane played Aracely in Retrato de Familia.
During 1996, Seoane played Sandra in Los Hijos de Nadie ("Nobody's Children"), where she acted with Puerto Rican Osvaldo Ríos. Seoane then acted in Cancion de Amor ("Love Song"), a soap opera geared towards teenagers and young adults. In it, she shared credits with young actors like Eduardo Capetillo, Jorge Salinas and Mauricio Islas, as well as with veterans such as Joaquín Cordero, Guillermo García Cantú, Lorena Rojas and Jaime Garza. Seoane played Roxana in Cancion de Amor.
Seoane continued on with her acting career in 1997, when she filmed Mi Pequeña Traviesa ("My Little Daredevil"), with Anahí, Rafael Inclan, Enrique Rocha and future spouses Hector Soberon and Michelle Vieth. Having given life to the character of Bárbara in that soap opera, Seoane then proceeded to take a two year lay-off from telenovelas after that. But she returned in 1999, when she had her first opportunity of starring in a telenovela, acting as Adriana in Amor Gitano ("Gypsy Love"), where Islas was her co-star. Seoane also acted in Tres Mujeres ("Three Women") that year, sharing the scene with Laura Flores as well as such up and coming actors as Dominika Paleta, Eduardo Verastegui and future husband and wife Bobby Larios and Niurka Marcos, among others. Seoane played Marcela Duran in Tres Mujeres.
After a two year hiatus from television, Seoane returned in 2001, making her comedy debut in Diseñador, Ambos Sexos ("Designer of both Sexes") a comedy about a fashion designer who pretended to be homosexual in order to get close to women.
Seoane played Ernestina Soto in Atrévete a Olvidarme ("Dare to Forget Me"), a telenovela which was also run during 2001, with Jorge Salinas and Adriana Fonseca as stars. Seoane has made a total of four soap operas where Salinas also acted.
In 2003, Seoane was offered her second starring role on a telenovela, when she participated as Rebeca Linares in Venevision's production, Rebeca.
Seoane then recorded her first CD, which was released during 2004. Sere Una Niña Buena ("I'll be a Good Girl"), her first discographic production, became a mild success in Seoane's show business career. It peaked at number 42 in the Top Latin Album in Billboard and her first single peaked at number 18 in the Hot Latin Tracks. Que no me faltes tu was her second single, which was successful, it peaked number 6 in the Hot Latin Tracks. Her second album was released in 2005, La nina buena ("The Good Girl"), it peaked number 38 in the Top Latin Albums in Billboard and the first single, Una de dos, reached number 22 in the Hot Latin Track; her second single was No vuelvo mas, which peaked 42 in the Hot Latin Tracks. In 2006 she released Con Sabor a... Mariana; the first single of this album was Mermelada. This album was less successful than the two previous albums. Her latest album was recorded in 2007, titled Mariana esta de fiesta... atrevete, and the single was Atrevete.
During 2005, a well known Hispanic gossip magazine in the United States sponsored a contest where winners would get a photo and a copy of the Sere una Niña Buena CD personally autographed by Seoane. Noting that three of the twenty contestants that won the prizes were from Puerto Rico, Seoane made sure to mention that country on her New Year's Eve Univision celebration show's speech.
As of 2006, Seoane was invited to appear on the famous telenovela, La fea más bella. She appears as Karla, who falls quickly in love with Fernando Mendiola, played by Jaime Camil.
At the end of 2007 Seoane personifies an evil villain in Juan Osorio's telenovela Tormenta en el Paraiso.
In November 2009 she stars in Nathalie Lartilleux's telenovela Mar de Amor.