Before he began his senior football career, Jack Lavery ('a nippy little player with an eye for goal', according to Martin Jarred and Malcolm Macdonald) was an apprentice mason. At 5ft 5½in tall, he is recorded as being the shortest plaer ever to feature in a senior team for Leeds City.

His playing days began in 1903 with Jarrow, a team who plied its trade in the Northern Alliance. At the end of the 1903/04 campaign he signed for Second Division Barnsley, though he got few first team chances with the South Yorkshire club, scoring twice in three games before moving on to Denaby United of the Midland League.

In March 1906, he returned to the Football League when he joined Leeds City. He was given his debut in the goalless draw at Clapton Orient on 29 March and remained in the side at inside-left through the final eight games, grabbing a couple of goals. After his performance against Gainsborough on 7 April, the Leeds Mercury reported: 'The outstanding feature of the game was the fine display of Lavery, who filled the inside-left position for Leeds. In attacking work the little Denaby man was quite brilliant, while he showed an enterprise and a desire for work which were highly commendable.'

Lavery was a regular choice throughout much of the 1906/07 campaign, scoring 12 times in 27 league appearances. The pick of his performances came when he bagged a hat trick in the 6-1 defeat of Stockport County on 15 December.

The following season he managed another 6 goals in 21 appearances for City, but at the end of the campaign departed for Swindon along with team mates Bob Jefferson and Harry Kay.

He stayed a couple of years with the Southern League club, scoring sixteen goals in 40 league games. Lavery was a member of the Robins side that reached the FA Cup semi-finals in 1910 where they lost to Newcastle United and he helped them win the Southern League title in 1911.

A few months later Lavery moved on to non-league North Shields where he ended his playing days.