He grew up in Lincolnville, Maine, and in 2000 graduated summa cum laude from Bard College at Simon's Rock with a B.A.

[6] Pariser's rise to prominence as a political activist began when he and college student David H. Pickering launched an online petition calling for a nonmilitary response to the attacks of September 11.

Pariser joined Moveon.org in November 2001, when founders Wes Boyd and Joan Blades invited him to merge his efforts with theirs.

Writing for The New York Times Magazine in 2003, journalist George Packer referred to MoveOn as the "mainstream" element of what "may be the fastest-growing protest movement in American history.

[13] In 2012, he co-founded Upworthy, a media company designed to make civically important ideas popular, with Peter Koechley.

[14] In 2018, with Professor Talia Stroud, he began work on Civic Signals,[15] with the goal of creating more “public-friendly” online spaces, a concept described in his 2019 Ted Talk.