Her debut as an actress was in the year 1997 when she was cast for a television show named Sin ti. The role she portrayed in the show is not known and it is believed to be a minor role. In the following year, she appeared in a minor role of Eloisa in the soap opera Angela. In the year 1999, she was seen on Por tu amor in a minor role of Alejandra Avellan.

She started working in several television shows after this. She is popular for portraying the role of Maria Zamudio in the television show Lo que la vida me robo in the year 2013. She has done several television shows in her career which includes Infierno en el paraiso in the year 1999, Clase 406 as Daniela Jimenez Robles in 2002, Angel rebelde as Luci Valderrama Covarrubias in 2004, Rebelde as Renata Lizaldi in 2004, Heridas de amor as Pamela Altamirano Villamil in 2006, Lola, erase una vez as Carlota Santa Domingo Torres-Oviedo in 2007, Alma de hierro as Melisa in 2008, Mujeres asesinas as Marcela Gonzalez in 2008, Verano de amor as Perla Gomez in 2009, Camaleaones as Silvana in 2009, Tiempo final as Paula in 2009, Cuando me enamoro as Matilde Lopez in 2010, Amorcito Corazon as Zoe Guerrero de Garcia de Alva in 2011, La Clinica as Maria Carlota in 2012, Noches Con Platanito as herself in 2013, Lo imperdonable as Virginia Prado Casteo in 2015 and Las amazonas as Casandra Santos in 2016.

In the year 2000, she made her film debut with the feature film El duende del reloj where she portrayed the role of Iris. She then went on to act in the movie Un mundo raro in the year 2001 where she portrayed the role of Edecan. Along with being an actress, Grettell Valdez is also a successful model and has worked with several big names of the industry.

Talking about her personal life, Valdez got married to Patricio Borghetti in the year 2004. Her husband Patricio was her co-star in the movies Angel Rebelde and Rebelde and also handled the soundtrack department. Valdez and her husband are proud parents of a son named Santino Borghetti who was born in the year 2008. In the year 2009, Valdez and Patricio had some differences and they filed for divorce. The couple got the divorce in the year 2010. She remained single for several years after her divorce, but in the year 2015, she started dating Horacio Pancheri. They have been together since then and have a loving relationship. According to her biography, her net worth is $1.5 million dollars.