The 36-year-old centre played in four World Cups for England, and had suggested he would make a decision after the defeat in last weekend's final to South Africa regarding his future.
But in extracts from Catt's autobiography, he said: "I had made up my mind it would be my last international.
"Others had come to the same decision. Nothing was said but everyone knew."
South Africa-born Catt still has two years left to run on his contract with Guinness Premiership side London Irish, and will operate in a player-coach role for the Exiles.
His appearance in the final - which was cut short by a calf injury - was his 75th for England. He also won one cap for the British and Irish Lions in 1997.