Gladis was born in Houston, Texas. He was raised in Farmington, Connecticut, the son of a sales and marketing executive and a state worker. He graduated from Farmington High School in 1995. Inspiration for a life of acting originated from the time he spent volunteering for theater productions at Miss Porter’s School, the internationally known all-girls school in town, where he knew male actors were needed. Most of his family is either Catholic or Christian, although his maternal grandfather was Jewish.

He started his college career at the SUNY School of Art Design at Alfred University before transferring to State University of New York at New Paltz, from which he earned a B.A. in theatre in 1999.

He provided the voice and MotionScan of Dudley Lynch in the game L.A. Noire and was Senior Seaman Yevgeny Borzenkov in the 2002 film K19: The Widowmaker. In 2015, he portrayed Lieutenant Matias in the science fiction action film Terminator Genisys.

As of July 10, 2016, Gladis was engaged to actress Beth Behrs. On July 21, 2018 they married at Moose Creek Ranch in Victor, Idaho, just outside Jackson Hole.