Blanchflower was born on 10 February 1926 in the Bloomfield district of Belfast, the first of five children born to John and Selina Blanchflower. His mother had played as a centre-forward on a women’s football team. He was educated at Ravenscroft public elementary school and was awarded a scholarship to Belfast College of Technology.

He left early to become an apprentice electrician at Gallaher’s cigarette factory in Belfast. He also joined the Air Raid Precautions (ARP) and in 1943 lied about his age to join the RAF. As a trainee navigator he was sent on a course to St Andrews University (where he acquired a lifelong love of golf) and in the spring of 1945 was posted to Canada for further training. By 1946, aged 20, he was back in Belfast, back at Gallaher’s, and building a reputation as an outstanding footballer. While at St Andrews Blanchflower played for the University College Dundee football team which was coached by former Celtic, Dundee United and Scotland trainer Jack Qusklay.

Blanchflower signed for Glentoran in 1946, before crossing the Irish Sea and signing for Barnsley for £6000 in 1949, at the age of 23. He transferred from Barnsley to Aston Villa for a fee of £15,000, making his debut in March 1951. He made 155 senior appearances for Villa (148 in the League), before being sold during the 1954–55 season.

Making his debut in 1949, he earned 56 caps for Northern Ireland, and in 1958 captained his country when they reached the quarter-finals of the World Cup. He was the first Irishman to achieve a half century of caps when he played against Wales in 1962.

In 1954 Blanchflower was bought by Tottenham Hotspur for a fee of £30,000, and during his ten years at White Hart Lane he made 337 League appearances, and 382 total appearances (scoring 21 goals). The highlight of his time at Spurs came with the 1960–61 season. With Blanchflower as captain Spurs won their first 11 games, a record for the top flight of English football and eventually won the league by 8 points. They then beat Leicester City in the final of the FA Cup to become the first team in the 20th century to win the League and Cup double, not achieved since Aston Villa in 1897.

On 4 December 1957 he captained the Northern Ireland team against Italy in Belfast, in a bad tempered game that came to be known as the “Battle of Belfast”; Blanchflower attempted to keep the peace as the game turned nasty.

Blanchflower was voted FWA Footballer of the Year in 1958 and 1961.

He was one of only a handful of players to have been awarded the title of FWA Footballer of the Year on two occasions, winning in both 1958 and 1961. He was one of many signatories in a letter to The Times on 17 July 1958 opposing ‘the policy of apartheid’ in international sport and defending ‘the principle of racial equality which is embodied in the Declaration of the Olympic Games’. On 6 February 1961, he also became the first person to turn down the invitation to appear on This Is Your Life, simply walking away from host Eamonn Andrews. Contrary to belief, this incident was not broadcast live on air, but was being recorded to be shown at the beginning of the live transmission. “I consider this programme to be an invasion of privacy”, he explained. “Nobody is going to press gang me into anything.”

Blanchflower commentated on a match for ITV as early as 3 January 1956 – the final of the Southern Junior Floodlit Cup between West Ham and Chelsea. He also hosted editions of the BBC’s Junior Sportsview in 1959. He was the colour commentator for the CBS television network broadcasts of National Professional Soccer League matches in the United States in 1967. His candour about the fledgling league’s shortcomings distressed network executives, as he recounted in a 10 June 1968 Sports Illustrated article he authored. In the 1968–69 season he was the regular commentator for Yorkshire Television.

In 1962 he helped Spurs win the FA Cup, scoring a penalty in the final against Burnley. In 1963 he captained his side to victory over Atlético Madrid in the final of the European Cup Winners’ Cup.

In 1965, Blanchflower briefly came out of retirement to play for Durban City. Blanchflower played three times for the club in the National Football League.

Following his retirement as a player, Blanchflower coached at Spurs for a number of years, and double-winning manager Bill Nicholson intended for Blanchflower to be his long-term successor. When Nicholson resigned from the club in 1974 however, Blanchflower found himself being passed over in favour of Terry Neill, and subsequently left the club himself. He became manager of Northern Ireland for a brief spell in 1978, and was then appointed as Chelsea boss. However, he won only five of his 32 games in charge and he left them in September 1979.

Anton Weinberg’s 1985 Channel 4 documentary film The Keller Instinct featured an appearance by Blanchflower, who spoke approvingly of his late friend musicologist Hans Keller’s advocacy of inventive, tactically creative football. He retired from his position as a writer for the Sunday Express in 1988.

On 1 May 1990, Tottenham held a testimonial match for him at White Hart Lane, but by this stage he was in the first stages of what would later be diagnosed as Alzheimer’s disease and Parkinson’s disease. He was eventually placed in a Cobham nursing home where he died as a result of pneumonia on 9 December 1993, aged 67.