Colin Cowherd during a live broadcast of his radio program on the campus of The University of Iowa in 2010.
In 2003, Cowherd was selected to replace Tony Kornheiser for the late morning time slot (10AM – 1PM ET) on ESPN Radio. His show, The Herd with Colin Cowherd is a syndicated talk radio show broadcast on ESPN Radio affiliates throughout the United States and online at ESPNRadio.com. In 2008, the Herd added a simulcast on ESPNU. The show features commentary on sports news, perspective on other news stories, and interviews with popular analysts and sports figures. Although a sports broadcast, he often reflects on personal life and business as it relates to the sports world.
Demographics and regional preferences are frequent topics of his program. The majority of his conversations primarily center around the National Football League (NFL) and college football with mentions of recent topics from Major League Baseball (MLB) and the National Basketball Association (NBA). He also has a featured segment, Spanning the Globe, during the second segment of his show.\ He, Michelle Beadle and later Charissa Thompson, co-hosted the TV show SportsNation on ESPN2 from 2009–2012; the show debuted on July 6, 2009. SportsNation was designed to take "the pulse" of the nation. Cowherd and Thompson were given two choices to select from and they attempted to determine which choice was the audience's favorite (e.g., Who is the better basketball player: Joe Kleine or Kerry Kittles?). Cowherd announced in September 2012 that he would be leaving the program; his last month as host was December 2012. He mentioned how he enjoyed doing radio work much more than television and wanted to focus exclusively on that in the future. Marcellus Wiley took over for Cowherd in January 2013. In fall of 2013, Cowherd began hosting the ESPN Sunday morning pro and college football talkshow Colin's New Football Show.
In 2013, Cowherd's first book, You Herd Me! I'll Say It If Nobody Else Will, was published. Cowherd has said on his radio show that he had been writing the book on-and-off for a few years.
Colin Cowherd during a live broadcast of The Herd at Public House in Chicago, Illinois on July 30, 2014.
Eddie Guerrero's death: In November 2005, Cowherd was criticized by former ESPN ombudsman, George Solomon for his treatment of the death of World Wrestling Entertainment (WWE) wrestler Eddie Guerrero. Cowherd was quoted as saying "he passed away doing steroids", implying that Guerrero's death had been caused by steroid use. According to Dr. Kathryn Berg, the assistant chief medical examiner for Hennepin County in Minnesota, the autopsy showed that Guerrero died from a hardening and narrowing of the arteries that supply blood and oxygen to the heart which can be caused by steroids. 
Using un-attributed material: In March 2006, Cowherd was criticized for using a joke on his show that was posted on the "M Zone", a University of Michigan fan blog without crediting it. Cowherd later apologized on-air and gave the M Zone full credit for the material. The M Zone response: "He was very cool about everything. This incident is now resolved and over."
The Herd knocks blog offline: On April 5, 2007, listeners of The Herd knocked The Big Lead blog site offline. Cowherd directed his listeners to access the web site home page simultaneously which resulted in a massive increase in traffic. The blog site's servers were not capable of handling so many users at one time so the site was knocked off-line for approximately 96 hours. ESPN's new Ombudsman, LeAnne Schreiber wrote an article sharing her (negative) opinion of Cowherd's actions. Schreiber contacted Traug Keller, a Senior Vice President at ESPN Radio, and Keller indicated that Cowherd would face no disciplinary action for the stunt, because there had been no policy against such a tactic at the time. To prevent this from happening again, Keller instituted a zero tolerance policy of such activities in the future.
Sean Taylor's murder: Cowherd was criticized for comments made regarding the circumstances surrounding Sean Taylor's death. On November 28, 2007, one day after Taylor's home invasion murder, Cowherd claimed that Taylor's past had brought this upon himself, and that Redskins fans who mourned him were not "grown ups". He stated about Taylor's turnaround; "Well, yeah, just because you clean the rug doesn't mean you got everything out. Sometimes you've got stains, stuff so deep it never ever leaves." Taylor's death was later found to be the result of a botched robbery, and the robbers hadn't known Taylor was home when they entered.
Kurt Warner interview: During an interview with Dan Patrick, Warner stated he would not want his children to play football professionally. Cowherd used this information in his broadcast. Patrick criticized Cowherd for not citing Dan's interview with Warner during his radio show.