Noted as a smooth and classy player, McKenney was signed as a teenager by Harold Cotton, the longtime head scout for the Boston Bruins.

[2] McKenney made his professional debut with the Bruins' American Hockey League Hershey Bears farm team in the 1953–54 season.

[4] McKenney was promoted to the Bruins in 1954, and made an immediate impact; he led the team in scoring in 1954–55, finishing second in Calder Memorial Trophy voting for rookie-of-the-year behind Ed Litzenberger of Chicago.

[7] 1959–60 proved to be McKenney's best season; in addition to the Lady Byng win, he led the league in assists, finished 8th in NHL scoring, and was voted to the Third All-Star Team.

He played effectively for the Blues, scoring 29 points in 39 games, before a knee injury caused management to send him down to the minors to rehab; it would prove to be his final NHL action.

In 1970, his playing career over, McKenney joined longtime Bruins teammate Fern Flaman on the coaching staff of the Northeastern University Huskies men's hockey team.

The couple settled in Braintree, Massachusetts, where they raised three Northeastern graduates, daughters Valerie and Deborah and son Scot, who played for the Huskies men's hockey team in the early 1980s.