The UH-1 Huey, a cargo-type helicopter, crashed Thursday evening, Maj. T.V. Johnson said.
Capt. Shawn Turner said Friday from Washington that three Marines were dead at the scene, and the fourth died later at a civilian hospital.
Victims' identities were withheld pending notification of their relatives.
The cause of the crash is under investigation.
"This certainly is a tragedy, and we hope we are able to assist the families of the victims during this time," Johnson said.
The versatile Huey, which played a major role during the Vietnam War, is widely used in military service. It is most often used in evacuations and moving supplies and troops. Some models can carry up to 12 passengers along with the two crew members.
In March, three Camp Pendleton Marines died when their UH-1N Huey crashed in Iraq. Another Huey crash two years ago killed two Camp Pendleton Marines on a training exercise in the mountains near the California-Arizona border.