Connecticut native Cosgrove made the trek to New York in the mid-nineties and has become a common sight on soaps ever since. He appeared on All My Children and nighttime soaper "Beverly Hills, 90210" before assuming the role of Bill Lewis III in June of 2002 on Guiding Light. During this time, he also made several appearances on film, including in 2002's hit Van Wilder.

After a trip to Primetime, Cosgrove returned to soaps with a highly popular revamp of his role on Guiding Light. After the CBS soap was canceled in 2009, Cosgrove portrayed Chris Hughes on As The World Turns until its cancellation in 2010. On December 27, 2010, Daniel returned to All My Children as Scott Chandler.

Days of our Lives - Aiden (January 22, 2014 - Monday November 9, 2015)
Person of Interest - Jeremy Watkins (2013 )
Jeremy Fink and the Meaning of Life - Herb Muldoun (2011)
Dirty Sexy Money - Freddy (2007)
Mattie Fresno and the Holoflux Universe - David (2007)
In Justice - Jon Lemonick (2006)
Guiding Light - Harlan Billy 'Bill' Lewis, III (2002 - 2005)
Van Wilder - Richard Bagg (2002)
The Way She Moves - Jason (2001)
All Souls - Dr. Brad Sterling (2001)
Valentine - Campbell Morris (2001)
They Crawl - Ted Gage (2001)
Artie - Frank Wilson (2000)
Beverly Hills, 90210 - Matt Durning (1998 - 2000)
Satan's School for Girls - Mark Lantch (2000)
Lucid Days in Hell - Dean (1999)
The Object of My Affection - Trotter Bull (1998)
All My Children - Scott Parker Chandler #3 (1996 - 1998)

Daytime Emmys Nomination, Outstanding Supporting Actor (2008)