Merediz was born in Guantánamo, Cuba on February 15, 1956. When she was five years old, she escaped from Cuba to Miami, Florida. Thereafter, she relocated with her family to Puerto Rico where she grew up. Merediz graduated with a bachelor's degree from Tulane University.

In addition to her Tony Award nomination, Merediz won a 2007 Drama Desk Award for Outstanding Ensemble Performance for her role in the off-Broadway run of In the Heights, as well as a 2003 HOLA Tespis Award from the Hispanic Organization of Latin Actors. At the 2008 Tony Awards, she received a nomination for Best Performance by a Featured Actress in a Musical for the Broadway incarnation of In the Heights.

In 2013, Latina magazine named her as one of the 50 Best Latin Singers and Pop Stars of All time. As per the magazine, “The Cuban Broadway star knows how to dominate a live stage and owns it!”

Her television credits include NBC's 2016 series "Shades of Blue" and Netflix's big hit Orange Is the New Black. In 2014, Merediz joined the cast of the George Lopez-starring FX series, Saint George, playing Alma, Lopez's mother. Her other television credits are Royal Pains, Blue Bloods, Pan Am, Law & Order SVU, The Sopranos, The Job, The George Lopez Show, Third Watch, Law & Order, and 100 Centre Street. She had recurring roles in both The Jury and Hope & Faith. Merediz also appeared on the pilot episode of the FOX TV series Past Life, as well as an episode of Throwdown with Bobby Flay as a judge.

Merediz’s motion picture credits include Top Five, The Place Beyond the Pines, The Angriest Man in Brooklyn, Mr. Popper's Penguins, Remember Me, K-Pax, Apartment 5-C, Trouble in the Heights, Like Sunday, Like Rain, Fugly!, Requiem for a Dream, Angie, Evita, and Changing Lanes. She worked with Meryl Streep in both Marvin's Room and Music of the Heart, and with Sidney Lumet in Q&A. Robert Redford directed her in The Milagro Beanfield War.