|Status||Deceased/Shot in the head by Peter Burke|
|Portrayed By||Ross McCall|
|Season(s)||1, 2, 3, 6|
|Last Appearance||Au Revoir|
|Episode Count||7 episodes|
|Images of Keller|
Keller is considered to be the blue-collar version of Neal Caffrey. The FBI has linked him to various misdeeds, from arms smuggling to stolen antiquities. Neal tells Peter Burke that Keller had pulled the Stockholm Airport robbery, having driven right up to a flight unloading Krugerrands and left fake bombs on the runway so that no one would follow him. Neal also reveals that he and Keller did a three-man job together that ended with Keller shooting the third man because of a misunderstanding regarding a passport being left behind. It was insinuated in later episodes that he left Neal alive because he was a 'worthy' opponent.
During the episode "Bottlenecked", Keller attempts to forge and auction a rare bottle of wine in order to pay off the members of the Russian mob that are after him. To get the attention of the FBI, he also murders an accomplice, who helped him steal several objects (at the time believed to help him forge the bottle) from the Museum of Natural History, by hitting him with a car. Neal takes on the challenge of forging his own rare bottle in an attempt to reveal Keller's as a counterfeit vessel. However, tests conducted by the auction house prove that Keller's bottle was authentic all along, and after making off with the money from its sale, he attempts to pay off the Russians and flee. Keller's plan is foiled and he is arrested when Neal and Peter catch him right before he boards a helicopter in Lower Manhattan, and reveal to him that the money supposedly pledged for the sale of his bottle was in fact a trick to draw him out of hiding. Keller later swears revenge on Neal, Peter, and the FBI.
While in prison, he orchestrated a complicated escape plan that involved kidnapping Peter to distract Neal and the FBI while he escaped during a prison transfer to avoid being killed by the Russians and disappeared into the wind. Later, after hearing rumors that Neal had acquired a vast treasure (the plunder of the Nazis during WWII), he returned to New York and attempted to trace the treasure's location, only to received a 6 million dollar bounty on his head (Mozzie's doing) and was almost killed when Raquel LaRoque took a shot at him while the FBI had him surrounded. Taking the opportunity to escape while the FBI was busy looking for his shooter, he went underground and kept a low profile while his wound healed.
Later, he appeared to Mozzie and asked him to tell him where the treasure was. Mozzie refused, and as a result, Keller kidnapped Elizabeth Burke and held her hostage in exchange for the treasure. Keller gives Peter and Neal 12 hours to give him the treasure, or he kills Elizabeth.
By that point, however, Mozzie has already moved the treasure from the warehouse and has disappeared without a trace. Luckily, Neal is able to deliver a message to Mozzie by using his carrier pigeon, Estelle. Enlightened of the circumstances, Mozzie agrees to help find Elizabeth, and together he, Neal, and Peter plan to con Keller in order to keep him occupied and give the FBI optimal time to find Elizabeth. To do so, Mozzie arranges a setup for two other conmen to be caught at the treasure's new location to trick the NYPD into cordoning off the area.
Meanwhile, Keller informs Elizabeth that the room she is being held in is very secure, with a bulletproof fire escape window and a lock that "even Neal couldn't pick". He then has his accomplice, Grant, guard her while Keller is off meeting Peter and Neal. When he actually meets with them, they reveal to him the location of the treasure. While they are on the scene, they are interrupted by the cops, who at the time were arresting the two conmen Mozzie set up to be caught. Keller immediately suspects Burke of a setup and threatens to kill his wife, but Peter and the gang manage to (temporarily) convince him that they are not at fault.
Keller then hatches a new plan: the four of them are to go back and help him steal the treasure. During the heist, Keller nearly succeeds in killing a cop who temporarily gets in their way, but is prevented from doing so by Neal. Eventually, their plan succeeds, but as soon as they are clear to move the treasure, Keller double-crosses Neal by knocking him out with an Egyptian cane pilfered from the stored treasure. Keller flees in the truck that Peter and the gang were using for the heist, with Neal unconscious in the back. Neal, however, quickly comes to and jettisons part of the treasure out of the back of the truck, causing Keller to stop and get out. Keller pulls a gun he had hidden under the truck and attempts to shoot Neal, who knocks the gun out of his hand with a gladiator shield (another object snaffled from the jettisoned treasure). They begin to duel, Keller using his Egyptian cane as a weapon instead. Neal has the upper hand in the battle until Keller whacks him with a Rafael painting, and beats him with his cane, but Peter arrives just in time to save Neal and inform Keller that Elizabeth has been saved. Peter attacks Keller; Keller then pulls out a knife in an attempt to kill Burke once and for all, but is prevented when Neal manages to shoot him in the leg. The FBI then arrives and they finally arrest Keller. Later, while in custody, it is revealed that Keller confessed to stealing the treasure in front of Russian authorities to make himself seem like a hero, in order to settle his debt with the Russian mob.
Matthew Keller is also shown to be a newer member of the Pink Panthers. Keller joined the Panthers while working for Interpol. Neal discovered Keller was working for Interpol in the episode Return to Sender. Interpol inserted a chip under the skin of Kellers wrist, leaving a painful scar and constant itching in his wrist.
He is also known for always being three steps ahead. Peter states that Keller "...knows our playbook better than we do..." Matthew is known to be smart with planning.
Keller met Neal at the Grand Casino in Monaco during the World Backgammon Finals. They pulled a three-man job together that ended with the third man being shot because of a misunderstanding with leaving a passport behind. It is also revealed in Season 3 Episode 11, Checkmate, that Neal and Keller were once friends.