Illingworth made his first-class debut at 19, was capped in 1955 and became a stalwart of the Yorkshire team in the 1960s. He made his Test début for England in 1958 but struggled on his first tour, in the West Indies in 1959–60, taking just five wickets in five Test matches. After failing to make an impact in four Tests against South Africa he found himself struggling for a place. A good series against India in 1967 established him in the team. He joined Leicestershire in 1968 after a contract dispute with Yorkshire.^{:250:194–195}

Illingworth played 787 first-class matches over nearly 33 years. As a bowler in county cricket, he took 2072 wickets. He sent down 408 balls without reward in the three Tests against New Zealand in 1973 but conceded only 1.91 runs an over in his Test career. He was not a sharp spinner of the ball, relying on accuracy and subtle variations of flight, but his arm ball was particularly effective with many of his victims being caught at slip, playing for spin that was not there. His middle-order batting was based around stern defence; a fifth of his innings, mostly from number 6 or 7 in the order, finished not out. He scored 24,134 first-class runs in all, with a best of 162, at an average of 28.06. Against the Rest of the World in 1970, Illingworth topped the England averages with 476 runs (52.89) and six half-centuries, a testament to his grit and determination against the best in the world.

The Yorkshireman was 'tough, combative, grudging, shrewd, and an instinctive reader of the game',^:194–195 and an experienced, no-nonsense captain who expected his team to play like professionals. David Gower wrote 'no matter how highly Ray might regard you as a player he would not have you in his team, come hell or high water, unless he was utterly convinced that you could do the job he had allocated to you'. He encouraged 'difficult' players like Geoff Boycott and John Snow who responded with their best Test form. 'Most of all, because he insisted on his "own side", he was able to get the best out of his players, both mentally and physically. He built up a tremendous team spirit which stood us in good stead on numerous occasions',^:80 and they tended to close ranks and treat the opposition, umpires, press and public as the enemy, an attitude that became prevalent amongst Test teams in the 1970s. In all he captained England in 31 Test matches, winning 12, losing 5 and drawing 14.

Illingworth only captained England for five seasons (1969–1973) but this was a successful period in English Cricket. Under Illingworth, England beat the West Indies 2–0 in 1969, held a powerful Rest of the World side to 3–1 in 1970, won the Ashes in Australia in 1970–71, beat Pakistan in 1971, somewhat surprisingly lost to India in 1971 but then regrouped and held on to the Ashes in a tight series in 1972 before eventually losing to a strong West Indies team in 1973.

Illingworth can perhaps be considered responsible for the victories in several of those tighter contests. For example at Headingley in 1969 the West Indies were 219 – 3 chasing 280 when Illingworth's inspired bowling change had Basil Butcher caught behind and wickets fell with just about every bowling change he made that afternoon. Similarly at Sydney in the 7th Test of the 1970–71 series it was Illingworth, deprived of his star batsman Geoff Boycott and his star bowler John Snow, who somehow pressurised the Australian batsmen into capitulation.

Those two matches will probably be remembered as Illingworth's finest moments as captain because they were the most famous. However it was for his brilliant tactics at Headingley in 1971 that he should receive most plaudits. With Pakistan needing only 231 to win – they were sailing toward victory with Sadiq Mohammad and Asif Iqbal in full command