A midfielder/defender, Lenarduzzi began his professional playing career at age 15 as a youth with Reading in the English Football League and went on to play 67 first-team games with the club, and scored two goals. Lenarduzzi then also joined the NASL Vancouver Whitecaps in 1974 in the team's first season. Until 1976 he divided his time between Vancouver in the summer and Reading in the winter. He played 11 seasons for Vancouver until the Whitecaps' last season in 1984, when the league folded. Lenarduzzi holds the record for most games played in the league, with 312. Lenarduzzi played all eleven positions during his tenure with the team. He was also voted NASL North American player of the year in 1978. The Whitecaps won the NASL Soccer Bowl championship in 1979. In 1984, Lenarduzzi joined the Tacoma Stars of Major Indoor Soccer League (MISL). He spent two seasons with them before moving to the Vancouver 86ers of the Canadian Soccer League in 1986 to become the team's Executive Director. In 1987, he returned to the field as a player and a coach with the 86ers.
Lenarduzzi earned 47 caps playing for Canada. He played all the country's matches both as the squad progressed to the quarterfinals of the 1984 Summer Olympics and as it participated in the first round of the 1986 World Cup finals.
Lenarduzzi resumed his pro career in 1987 as a player/coach with the newly formed Vancouver 86ers of the newly founded Canadian Soccer League. After retiring permanently from playing in September 1988, he continued to coach the 86ers for the next five seasons. He led the franchise to an unprecedented four consecutive CSL titles from 1988 to 1991. His team set a record for professional North American sports teams when the team went 46 games unbeaten between June 6, 1988 and August 8, 1989. His 86ers career totals of 96wins-24loses-28ties makes him the winningest coach in Vancouver professional sports history.
Lenarduzzi became head coach of the men's national team in 1993. In his first of two bids to see Canada back through to a World Cup finals, his squad twice came close but failed to progress to the 1994 finals. First they lost at home to Mexico despite scoring the game's first goal in a game with which Canada could have gone through to the finals with a win. (See 1994 FIFA World Cup qualification (CONCACAF).) As CONCACAF qualifying winners-up, Canada then lost the away leg to Australia in a match decided by penalty kicks that saw the winner of the home-and-away series go on to play Argentina in a home-and-away series for a finals spot (won by Argentina).
In qualifying for the 1998 finals, Canada failed to finish in the top three of a six-nation CONCACAF final qualifying round league tournament and progress. (See 1998 FIFA World Cup qualification (CONCACAF).) Lenarduzzi subsequently resigned his post in 1997.
Lenarduzzi served as 86ers general manager from 1988 to 1993. He resumed the post in 1998 and was named the A-League's executive of the year for 2000. In 2001 he also assumed the position of the Whitecaps Head of Soccer Operations. (The 86ers changed their name to Whitecaps in 2001.)
During the 2008 MLS season Lenarduzzi served as colour commentator during CBC's Toronto FC broadcasts before Jason DeVos arrived to fill the position on a more permanent basis.