Born Arnold Cream in Merchantville, Walcott took the name of his boxing idol, Joe Walcott, the welterweight champion from Barbados. He turned pro in 1930 at the age of 16 and embarked on a slow, steady, rise to the top. He won the heavyweight title on his fifth try, at the age of 37. He held the record for oldest heavyweight champion until 45-year-old George Foreman won the crown in 1994. Early in his career, Walcott lost a pair of fights to “Tiger” Jack Fox and was knocked out by contender Abe Simon. But in 1945, Walcott beat top heavyweights such as Joe Baksi, Lee Q. Murray, Curtis Sheppard and Jimmy Bivins.

Walcott, considered an excellent boxer and slick defensive fighter, challenged Joe Louis for the title in December 1947 at Madison Square Garden. He twice knocked Louis to the canvas, but lost a 15-round split decision to the champion. Louis won again in 1948, knocking Walcott out in 11 rounds. When Louis retired, Walcott and Ezzard Charles met for the vacant heavyweight title in 1949, a bout that Charles won in a 15-round decision. Walcott beat future Hall of Famer Harold Johnson in 1950 and fought Charles twice more in 1951, losing the first but scoring a seventh-round knockout the second time to finally win the heavyweight title.

Walcott fought Charles for a fourth time, earning a decision in his first title defense. But he lost his second defense to Rocky Marciano. He retired after Marciano knocked him out in the first round of their 1953 rematch. Walcott remained active in boxing as a referee and later as the chairman of the New Jersey State Athletic Commission. Walcott later turned to politics, and was elected to the office of Sheriff of Camden County in 1971, serving for three years. He also served as the chairman of the New Jersey State Athletic Commission.