Sam Fisher was a member of Third Echelon, a top-secret sub-branch within the National Security Agency (NSA). He is 177 cm (5 feet 10 inches) tall, weighs 78 kg (170 pounds),[1] has greying brown hair and green eyes. He was the first person to be recruited for field operative of the "Splinter Cell" program for Third Echelon. Fisher is an expert in the art of stealth, trained in various techniques and tactics, and highly trained in fieldcraft. He is also an expert in the Israeli hand-to-hand combat system of Krav Maga.[2] In Splinter Cell: Conviction, he utilized the Center Axis Relock, a modern gun-fighting technique used in close quarters combat. He prefers to work alone in the field. When not on assignment or at Fort Meade, Fisher resided in a townhouse in Towson, Maryland.

Fisher was born on August 8, 1957[3] in Towson, Maryland.[4] While not much is known about his early life, it is known that Fisher attended a military boarding school shortly after his parents died when he was a child. He later graduated from the United States Naval Academy with a Bachelor's degree in Political Science. While Fisher was stationed at an U.S. Air Force Base in Germany during the 1980s, he met Regan Burns and they married in 1984. They had one daughter together, Sarah (born May 31, 1985 in Frankfurt, Germany).[5] Fisher and Regan later divorced and she had Sarah's surname changed. Regan died from ovarian cancer sometime in 2000[6] and Sarah was killed by a "drunk driver" in September 2008. However, it was established that the death of his daughter was no accident. After learning this, Fisher attempts to uncover why his daughter was murdered, and what connections it has to Third Echelon, which has become bogged down with red tape to the point of ineffectiveness and corruption. It is soon revealed that Sarah is alive and would have been used as leverage to frame Sam for an unsuccessful coup against the U.S. President.

Sam's direct supervisor and handler was Colonel Irving Lambert, USA (Ret.) (deceased), who coordinated intelligence and objective updates with Fisher during his missions. In addition to being supported by Lambert, Sam was also accompanied and supported on operations by NSA employees Vernon 'Junior' Wilkes (deceased), Anna Grímsdóttir, Frances Coen and William Redding (introduced in Chaos Theory). One of his aides, Dermot Paul ("D.P.") Brunton (introduced in Pandora Tomorrow), became the head of SHADOWNET Operations, a black-ops group within Third Echelon which uses teams of operatives.

Fisher has conducted operations in Canada, the Democratic Republic of Congo, China, Iceland, Israel, East Timor, Indonesia, Japan, Kyrgyzstan, Russia, Ukraine, Turkey, Azerbaijan, Iraq, North and South Korea, Mexico, Panama, Peru, Myanmar, Serbia, the Republic of Georgia, and France in order to complete his missions. He has also conducted operations inside the United States, places such as LAX International Airport in Los Angeles, California, New York City, New Orleans, Washington D.C., Ellsworth Federal Penitentiary in Kansas and the CIA headquarters in Langley, Virginia.

Ubisoft's lead character artist Martin Caya established in early interviews about the first game of the series that during his career Fisher had served in Afghanistan, where he had an experience in which he was forced to hide under dead bodies in order to avoid being killed in the middle of an operation. Caya also established that Fisher had served in East Germany and in "other Soviet satellite countries leading up to the collapse of the USSR."

The novel version of Tom Clancy's Splinter Cell establishes that Sam hated his time in the CIA, and that he mostly had official cover (i.e. he was a "diplomatic aide"). The "Bank" mission in Chaos Theory established that Fisher served in Panama during Operation Just Cause when Redding reveals in the level's pre-mission briefing that Fisher was part of a CIA team that raided the same bank during the conflict searching for some of Noriega's drug money. The "Bank" mission also established that he served in Kuwait, where he said he spent the months leading up to the Gulf War "sleeping in a ditch on the road between Baghdad and Kuwait" shortly after the invasion ended in 1990. The end of the training mission in Tom Clancy's Splinter Cell established that he saw action during the Gulf War in 1991 and was active in Kuwait when Lambert tells Sam "I hope you don't mind I told him ['Junior' Wilkes] some of your stories from Kuwait". Wilkes makes a comment stating "I've heard crazy things about your work".

It was revealed during the flashback level in the series' fifth installment, Splinter Cell: Conviction, that Sam served in southern Iraq during the Liberation of Kuwait campaign when he led a four-man SEAL squad on an operation, which during he and his team was ambushed by Iraqi forces while patrolling a highway along the Al Diwaniyah-Basra border during Operation Desert Storm. Although Sam survived, two of his teammates were killed, and he was subsequently captured. However, his teammate and second-in-command, Victor Coste (callsign "Husky"), who survived the ambush and was left for dead, rescued him after he fought his way through several Iraqi soldiers in order to reach Fisher, who was being tortured for information regarding their mission in the region.

The novel Splinter Cell: Checkmate revealed that Sam served in Senegal where his team was deployed to hunt down and assassinate a French black market arms dealer who had been arming both sides of a brush war between Senegal and Mauritania. Fisher’s team eventually tracked down the arms dealer in Dakar where they eliminated him after weeks of searching through the jungles along the Senegal-Mali border.[7]

Shortly after Fisher rescues Douglas Shetland from a hostage situation during the "East Timor" mission in the second game, Splinter Cell: Pandora Tomorrow, Shetland established that Fisher had served with the Navy SEALs when he asks Sam "Where are the rest of the SEALs?" to which Sam replies and establishing that he left the Navy in 1996 by saying "I came alone. Haven't been Navy for a decade." It's also been established in the original Splinter Cell in the interview with Sam found in the extra features that he was indeed with the Navy SEALs, when he says "I've had the good fortune in my life to work with some really talented and professional people. U.S. Navy SEALs, the folks at Third Echelon. All real pros." The "Sam Fisher Interview" was an exclusive behind-the-scenes video with Sam going undercover as Ubisoft's "technical advisor" after the "Presidential Palace" level. According to his DD214 from the website for Double Agent, Sam rose to the rank of Lieutenant Commander (O-4) in the Navy, where at some point he spent nearly three years (2 years, 11 months) as an intelligence officer[8].