At age 11, while Redknapp was playing for East London Schools football, he was spotted by Dickie Walker, a Tottenham Hotspur scout. From there, Redknapp grew in the Tottenham youth ranks playing at Cheshunt, meeting the likes of Bill Nicholson, Dave Mackay and Danny Blanchflower. At age 15, Redknapp moved to West Ham United and played alongside Bobby Moore. In a 2008 interview, Redknapp stated as part of a tribute to Tom Finney, "I was a big Arsenal fan as a kid and I remember seeing him play against Tommy Docherty one night."
After being appointed Tottenham manager later in 2008, Redknapp stressed his Tottenham connections as well, stating:
In January 2008, it emerged through the media that Redknapp was offered the vacant manager's job at Newcastle United following the sacking of Sam Allardyce. Redknapp had apparently declined the job, stating, "I have a job to do to take this club forward and to walk away would not have been the right thing to do." It was later stated by Newcastle chairman Christopher Mort that Redknapp "was interviewed for the job but he was only one of a number of people we were speaking to at that time", and at the time of Redknapp's interview the club had already been in secret talks with the eventual appointee, Kevin Keegan, for a week.
On 8 March 2008, Redknapp led Portsmouth to an FA Cup quarter-final victory over Manchester United, completing a hat-trick of FA Cup wins over Manchester United, and followed this with a semi-final victory over West Bromwich Albion at Wembley Stadium on 5 April. He guided the club to their first FA Cup Final in 69 years, where they defeated Cardiff City on 17 May 2008 to win The FA Cup 1–0, thanks to a goal scored by Nwankwo Kanu. He is the last English manager to win a major English trophy.
Redknapp returned to Portsmouth to receive the Freedom of the City in a ceremony on 28 October 2008. As this event took place two days after his departure for Tottenham Hotspur, he received a mixed reception from the Portsmouth fans, despite having led the club to a long-awaited trophy in the 2008 FA Cup.
In October 2008, following the sacking of Juande Ramos by Tottenham Hotspur, the club announced Redknapp had agreed to take over as the new manager at Spurs, the club where he began his playing career. Tottenham paid £5 million in compensation to Portsmouth for releasing Redknapp. Spurs had secured only two points from the first eight matches of the season prior to Redknapp's arrival and lay bottom of the Premier League table, but in his first two weeks in charge, he took the club out of the relegation zone, winning 10 out of the 12 points available after wins against Bolton Wanderers, Liverpool and Manchester City, as well as a remarkable 4–4 draw against North London rivals Arsenal.