[1] His father, Sal, was employed at a tool and die shop and was eventually promoted to plant manager.

He threw a no-hitter against Winthrop High School in April 1964, several days after his brother Tony made his major league debut.

[4] He made his Major League Baseball debut on April 11, 1969, at the age of 21,[1] entering as a pinch runner and stealing a base in a 2–1 extra-innings win over the Cleveland Indians.

[1] In order to fit Conigliaro into their lineup that year, the Red Sox moved Carl Yastrzemski to first base.

[2][8] Billy Conigliaro reportedly became "very emotional" when his brother Tony was traded to the California Angels at the end of the season.

[1] Conigliaro was part of a ten-player trade that sent him, George Scott, Jim Lonborg, Ken Brett, Joe Lahoud, and Don Pavletich from the Red Sox to the Milwaukee Brewers for Tommy Harper, Marty Pattin, Lew Krausse, and minor-league outfielder Pat Skrable on October 10, 1971.