Garayua moved to California in 2004 after being cast in the leading role in Nilo Cruz's Two Sisters and A Piano at the Old Globe Theater in San Diego. Afterwards, she moved to the greater Los Angeles area and was cast for a minor role in Fun With Dick and Jane after only 2 weeks. During this time she also appeared in an episode of NYPD Blue as a guest star.

Garayua has worked as a private acting coach in the Los Angeles area since 2005. She has also taught “Beginning and Intermediate Drama” at the Los Angeles Unified School District's “Gifted and Talented Fine Arts Conservatory", “Adult Beginner’s Scene Study” at “The Mauricio Ochmann Studio” in North Hollywood, “Advanced On-Camera Technique” at “Actor Training in LA” in North Hollywood, and “Teen Scene Study” at the “John D’Aquino’s Acting Studio” in Toluca Lake.

In 2007, Garayua guest starred in an episode of Grey's Anatomy as an Intern named Graciella. She would ultimately become a recurring guest star in the show, appearing in a total of 24 episodes from 2007 to 2010. In 2008 she played the part of Reyna in two episodes of Showtime's Weeds titled No Man is Pudding and The Three Coolers.

Garayua was nominated for Best Female Principal Performer by the San Francisco Bay Area Theater Critics Circle in 2009.

Fixing Paco, in which Garayua played the lead role of Margie Fuentes, was nominated for 2013 Best Webseries in the "Drama" Category. The show was also nominated in 2014 to the Best WebSeries in 3 categories, "Drama", "Comedy", and "Reality or Informational.

Other notable roles include Nurse Chapel in American Housewife, Madison Young in Criminal Minds, Vita Chacon in Cold Case, and Gloria Ortiz in ER. As of 2016, Garayua has worked in over 25 different television shows.

Gloria Garayua was born and raised in the Fordham section of the Bronx. Garayua is of Puerto Rican heritage and her parents are from Ponce, Puerto Rico. She attended St. Nicholas of Tolentine Elementary School and St. Catherine’s Academy High School, both in the Bronx.