Antonio Acosta Hernandez, alias "El Diego," is "the mastermind behind the US consulate killings," federal police anti-drug chief Ramon Pequeno told reporters.
He was referring to the March 2010 murder of a US consular officer, her husband and another American in Ciudad Juarez, a border city opposite El Paso, Texas.
Acosta also was blamed for the killing of 14 youths at a January 2010 party, a July 2010 car bomb attack that left two policemen dead and killings at a rehabilitation center for addicts that targeted several alleged members of rival gangs.
Acosta was arrested Friday after a shoot-out in the northern city of Chihuahua.
He was a leader of "La Linea," an armed wing of the Gulf cartel, and had links to other gangs such as "Los Aztecas." He had a $1.2 million bounty on his head.
Pequeno credited Acosta with raising the level of "violence and radicalism" in a rivalry between the Gulf cartel and its rivals for control of smuggling routes into the United States.
According to official figures, an estimated 41,000 people have been killed in violence related to organized crime in Mexico since December 2006, when President Felipe Calderon put the military in charge of a crackdown on the drug cartels.
Ciudad Juarez, where Acosta operated, is considered the most violent city in Mexico. Last year, the city saw 3,100 murders linked to drug trafficking.