Dennis Abbott is an FBI Special Agent who has become a series regular, along with FBI agent Kim Fischer, to replace the departing Special Agents Wayne Rigsby and Grace Van Pelt. He is described being calm in the face of a crisis but he is not one to be angered. He is an Iraq war veteran of African-American descent. He made his first appearance in the sixth season episode The Great Red Dragon.
Born and raised in the Longhorn state, Abbott grew up a protector. His mother and father, at an early age, raised Abbott to think of others regardless of personal consequences. So after college, Abbott joined the FBI to help as many people as he could. At the beginning of his career he proved himself solving narcotics and arms cases along the Mexico border working with the DEA. While dangerous, it was worth it when the FBI rewarded him with his own team at the Austin office. Abbott’s years of experience taught him that a great leader was only as good as his team. To that end, he spent the last few years assembling a skilled team of investigators that were willing to bend the rules to protect the innocent. When his team was called in to investigate a massive conspiracy within the California Bureau of Investigation, Abbott met many good agents caught in bad circumstances. When the dust had settled, Abbott invited Kimball Cho, because of his skills and his relationship with Patrick Jane, to work with him in Austin. But getting Jane and Lisbon to join his team took more work. Enlisting the help of his best agent, Kim Fischer, Abbott tracked down Jane first and soon Lisbon followed. Now he has assembled his perfect team and the real test begins.
Abbott is the FBI agent from the Austin, Texas bureau who was sent and authorized to dismantle CBI (California Bureau of Investigation) and relieve all agents from active service (apparently indefinitely), including Lisbon, Cho, Rigsby and Van Pelt, as well as consultant Patrick Jane, after Jane's epic public revelation, captured by the media whom he addresses, declaring that Gale Bertram, the director of the CBI, is serial killer Red John.
Jane's own personal belongings are being removed and the cup he happens to be holding falls and breaks. Jane declares with great sadness that it was his "favorite teacup".
While Abbott gives Patrick a lot of freedom in solving cases, it is proved that he is no dunce himself when he recognises Patrick's true feelings for Lisbon before any of the other characters.
In this season his personal and professional life are explored in more detail. His wife Lena is up for a job as the Undersecretary for the Department of Commerce and he is interviewed by a supporter of her appointment. It is briefly mentioned that Abbott previously worked for a joint FBI-DEA task force called Rio Bravo and something happened that Abbott doesn't want to talk about.
When his ex-boss DEA agent Bill Peterson starts blackmailing him using the information he reveals to Jane that he murdered a commander of a local drug cartel known as the Zetas to prevent him from massacring everyone on a bus and quits the next day. Bill eventually put the pieces together and kept quiet. Abbott and Jane eventually decide to work together to get him out from under Bill's thumb.