Danny was born in in Dunraven Park, in the Bloomfield district of Belfast, possibly inheriting some footballing ability from his mother, who had played as a centre-forward in a women's team. He was the first of five children - three boys, two girls in a typical working class Presbyterian family. He was educated at Ravenscroft Public Elementary school and was awarded a scholarship to Belfast College of Technology. His first exposure to the game came when he played for a representative Belfast Cubs side against the Dublin Colts in 1937. His footballing hero was known to be Peter Doherty, who began his career with Glentoran and left for Blackpool, before then moving to Manchester City.

He left Belfast College early to become an apprentice electrician at the Gallachers' cigarette factory. He also joined the air-raid precautions (ARP) and in 1943 lied about his age in order to join the RAF. As a trainee navigator he was sent on a course to St Andrews University and during his time there as well as playing for the University football team, he was introduced to the game of golf and his love of this past time was to stay with him forever. In 1945 he was posted to Canada for further training, but was soon recalled as the war came to a close. By 1946 he was back in Belfast, back at Gallachers, and building a reputation as an outstanding footballer.

He made his professional debut with Irish side Glentoran in 1946 and was transferred to Barnsley in 1949 for £6,500. Two years later he moved on to Aston Villa for £15,000 and his travelling came to an end in 1954 when disillusioned with Villa's lack of ambition he joined Tottenham Hotspur for £30,000, at the age of 28. Danny was signed by then manager Spurs Arthur Rowe, who was soon replaced by Jimmy Anderson who was to act as a stop gap before the appointment of Bill Nicholson.

Following his appointment, new manager Bill Nicholson set about putting together a team which was to be without equal in the era and the side was to be created around the stylish and visionary Blanchflower, who insisted that the 'double' of League and FA Cup was attainable. They did achieve that double in 1961 when Danny and Spurs were unstoppable as they became the first twentieth century team to win the double. This was also the year when Danny became famous for being the first British person to turn down the "red book" on the British 'This is Your Life' show in February 1961. The next year Spurs won the FA Cup again and reached the semi final of the European Cup against Benfica. In one of the most exciting games ever seen at White Hart Lane, Spurs came back from a 3-1 first leg deficit and an early goal conceded in the second leg to score two goals, one coming almost inevitably from a Danny Blanchflower penalty and they hit the woodwork three times, but just failed to get the third.  The following year, they reached the final of the European Cup Winners Cup mostly without an injured Blanchflower, but he was back for the big game and helped by pain killing injections, he inspired Spurs to a 5-1 drubbing of Atlético Madrid.

Danny's talents had inevitably been recognised by Northern Ireland and he received his first cap in 1949 against Scotland, gaining a total of 56 caps. His proudest international moment being the 1958 World Cup finals where he captained the Irish to the quarter finals only to be beaten soundly by France.

By 1964, the Spurs team was beginning to disintegrate and Danny at the age of 37 and suffering from a chronic knee injury decided to retire. He moved into a successful career in broadcasting and journalism and a rather less successful career in management. In 1974 when Bill Nicholson eventually retired as Spurs manager he was unsuccessfully touted as a replacement. He was though appointed briefly as manager of Northern Ireland in 1978 and he was manager of Chelsea in the 1978-1979 season, where they won just 5 out of 32 games as the club rocketed down the table. He eventually left the job less than a year after his appointment, in September 1979.