Cohen gained national notoriety for a 1967 altercation with Frank Sinatra at the Sands, in which he responded to the singer's drunken and aggressive behavior by punching him in the mouth and knocking the caps off his front teeth.

He began his career as a bookie and an operator in illegal gambling clubs run by the Mayfield Road Mob in that city.

One night, El Rancho owner Beldon Katleman was inspecting the packed casino when he noticed a man dressed in jeans and tennis shoes sitting beside the well-heeled high rollers at the gaming tables.

[17] Cohen provided employment at the Sands for family members: he hired his brother Mike to repair slot machines and later to deal cards,[12] and his cousin H. Lee Barnes for an accounting position.

[12] In 1963 the FBI released to the Justice Department transcripts of conversations acquired through its illegal wiretapping of the homes and offices of 25 Las Vegas gambling executives connected with the mob.

[19][20] Cohen was the target of an attack by Frank Sinatra on Monday, September 11, 1967, after the singer's casino credit had been stopped on the orders of Howard Hughes, who had purchased the Sands earlier that year.

He yelled at the pit bosses, destroyed the furniture in his penthouse apartment, steered a baggage cart through a plate-glass window in the shopping arcade, and ripped wires out of the hotel switchboard before leaving.

Sinatra confronted him there, unleashed a stream of curses and threats including, according to witnesses, an anti-Semitic slur,[23] and upended the table laden with breakfast onto Cohen, spilling a potful of hot coffee on him.

[21][22] Robert Maheu, chief executive of Nevada operations for Howard Hughes, informed his boss that Sinatra had been drinking and gambling excessively into the early morning hours for two nights straight.

Maheu stated in his report:[25] At six a.m. today, Sinatra appeared at the Sands, made one hell of a scene and insisted on seeing Carl Cohen.

In the November municipal elections that year, posters appeared with pictures of Sinatra "with his front teeth blackened out" and the slogan, "Carl Cohen for Mayor".