Johnny stood just 5 ft 4 ins tall, weighed around 10 stone and wore a size 2 boot, yet he could unleash some rocketing shots especially from dead-ball situations. He could occupy either flank but the right hand side was undoubtedly his best. When he was 15 he served with Oakengates Town and then in 1938 he turned professional with Walsall, who had been following his progress since 1934. During the war he became a P.T. Instructor in the Army and had several games for the Western Command and Army sides in various friendly matches. He also played from time to time for the Saddlers and when available guested for a few clubs.

Then in May 1946 Wolves paid £4,000 to bring him to Molineux and he made his debut in the 6-1 win over Arsenal on the opening day of the 1946-47 season. The following season he was the clubs joint top goal scorer with 16 goals, and in 1949 he won a FA Cup winners medal when Wolves beat Leicester City 3-1 at Wembley. His form that season led to him winning his first of three full caps for England when he scored twice in a 6-0 win over Switzerland at Highbury in 1948. His other 2 international outgoings were against Wales (WCQ) in 1949 and v Yugoslavia in 1950. He also played for the Football League Xl.

He netted his first hat-trick for Wolves in December 1950 in a 3-1 home win over WBA and his second when Wolves beat Chelsea 8-1 during the clubs League Championship winning season of 1953-54. The following season, Hancocks was the clubs leading scorer with 26 goals in 32 games including hat-tricks against Huddersfield Town (home 6-4) and Arsenal (home 3-1). Hancocks topped the goalscoring charts again in 1955-56 when his total of 18 goals in 28 games included his fifth and final hat-trick for Wolves in a 9-1 win at Cardiff City. Sadly it was his last season in the first team, and after scoring 168 goals in 378 league and cup games, he spent a season in the clubs Central League side before becomming player-manager of Wellington Town in the summer of 1957, but then gave up the managerial tag in September 1959. He quit as a player 3 months later.

In January 1960 Johnny teamed up with Cambridge United; he switched to Owestry Town in July of that year and ended his playing days with GKN Sankey's in the 1960-61 season. In later years he worked full-time at Maddock & Sons (Ironfounders) in his native Oakengates, taking retirement on his 60th birthday in 1979.