In 2010, he participated in NBC's The Sing Off, working with music director Deke Sharon and receiving acclaim from The Sing-Off judges Shawn Stockman, Nicole Scherzinger and Ben Folds for solo performances leading his group, On The Rocks – the first official collegiate a cappella group in Oregon.

Hollens's recordings include tracks for "The Sing-Off Season 2-Greatest Hits" as well as many collegiate a cappella albums for such groups as On the Rocks, Divisi, Cornell's Chordials, the Duke's Men of Yale and the Whiffenpoofs.

[9] He has also recorded Sing-Off Season 2 winners, Committed, the Backbeats, and the Grammy Award-winning group The Swingle Singers.

To support his musical endeavors, Hollens joined the newly founded crowdfunding platform Patreon in 2013.

In 2015, he performed guest lead vocals for Brian Wilson's album No Pier Pressure on the song "Our Special Love".

[17] In 2016, Hollens teamed up with Home Free, the winners of The Sing-Off Season 4, to record an all-vocal arrangement of the hymn "Amazing Grace".

"I had the absolute honor of working with Home Free on this one," Hollens states in a video message at the close of the song's YouTube release.