He was a recurring cast member in the first two seasons of the Showtime American television drama series Masters of Sex.

Grunberg had a major role in the NBC TV show Heroes as telepathic police officer Matt Parkman.

[10][non-primary source needed] He took up a minor role in the 2011 neo-noir detective videogame L.A. Noire, in which he provided both voice and facial motion capture as murder suspect Hugo Moller.

On November 7, 2011, he appeared as a guest star on an episode of the TV series Hawaii Five-0 with former Heroes co-star Masi Oka.

[11] In 2013, Grunberg appeared in one episode during the first season of the TV series Masters of Sex as the character Gene Moretti, a rich business man.

[12] In February 2016, Grunberg co-hosted a late night talk show with Kevin Smith titled Geeking Out on AMC.

[19] In the past, this has included events such as an auction of guitars handpainted by celebrities such as Donald Trump, Pink and Grunberg's Alias co-stars Jennifer Garner and Michael Vartan.

[20] In 2009, Grunberg launched Talk About It, a website dedicated to epilepsy education and awareness, featuring many of his co-stars and celebrity friends,[18] including Garner, Larter, Pasdar, Ramamurthy, Ventimiglia, and Panettiere, as well as Zachary Quinto, Chris Pine, Drew Pinsky, Ron Rifkin, and John Mayer.