Chalker began his military service with the U.S. Army, serving in the 82nd Airborne Division. Upon discharge he tried his hand at a few civilian jobs and found them less than challenging, Chalker then joined the United States Navy to become a Navy SEAL where he eventually rose to the rank of Command Master Chief of Naval Special Warfare Center(NWSC BUD/S) and retired as an E-9.
Chalker initially served with SEAL Team One and was hand-selected by Commander Richard Marcinko to become a Plankowner member of the Navy's first dedicated counter-terrorist unit, SEAL Team Six. As a member of SEAL Team Six, he participated in a mission during Operation Urgent Fury in the US Invasion of Grenada. His team reached then Governor General Paul Scoon's mansion and held it for an entire day while being attacked by a force of Grenadians and Cubans.
As a SEAL, Chalker also saw action in Haiti (recounted in his book One Perfect Op), El Salvador, and Panama.
When Marcinko was tasked to select members for a new unit to test security at US Naval Bases against the threat of terrorism, he once again chose Chalker as one of the founding members. This unit was called Red Cell.
After Red Cell was disbanded Chalker transitioned back to SEAL Team Six and eventually received the assignment to become the Command Master Chief at the Training Center Command for BUD/S (Basic Underwater Demolition/SEALs) Training in Coronado, California.
While serving at BUD/S as Command Master Chief, Chalker was hired as a technical advisor for The Rock, a 1996 Jerry Bruckheimer film. Chalker was also used as an onscreen extra during the movie's swim and dive sequences. This led to a position as Director of Operations with Global Studies Group, Inc. (GSGI), upon his retirement from the US Navy. GSGI is a combination security and training company owned by former US Navy SEAL Harry Humphries that specializes in bringing modified (civilian version) SpecOps tactical skill training to law- enforcement agencies and Hollywood movie productions.
Chalker is also credited for inventing and developing a tactical rifle and submachine gun sling known as the Chalker Sling while at SEAL Team Six. The Chalker Sling attaches the long gun to the shooter via a harness which enables the operator to quickly transition to a secondary weapon or perform another task while using both hands and keeping the weapon in a close-ready position as the weapon "hangs" from the chest, leaving just enough slack to be able to quickly bring it to firing position with little effort.
Since retiring from the Navy, Chalker has authored six books, three fiction and three non-fiction with Kevin Dockery about life as a Navy SEAL.
Chalker, Dennis C. One Perfect Op : an Insider’s Account of the Navy Seal Special Warfare Teams / by Dennis Chalker with Kevin Dockery. 1st ed. New York : Morrow, c2002. xiii, 332 p. ; 25 cm. ISBN 0-380-97804-0 (acid-free paper)
Chalker, Dennis C. Hell Week : SEALS in Training / Dennis Chalker with Kevin Dockery. New York : Avon Books, 2002. 375 p. ; 18 cm. ISBN 0-06-000148-8
Chalker, Dennis C. The United States Navy SEALs Workout Guide : the Exercise and Fitness Programs Based on the U.S. Navy SEALs and BUD/S Training / Dennis C. Chalker, with Kevin Dockery. 1st ed. New York : William Morrow & Co., 1998. xxii, 183 p. : ill. ; 28 cm. ISBN 0-688-15862-5
Chalker, Dennis C. The Home Team : Undeclared War / Dennis Chalker with Kevin Dockery. New York : Avon Books, c2004. 392 p. ; 18 cm. ISBN 0-06-051726-3
Chalker, Dennis C. The Home Team : Hostile Borders / Dennis Chalker with Kevin Dockery. New York : Avon Books, c2005. 362 p. ; 18 cm. ISBN 0-06-051727-1