The Zimbabwean was heavily criticised after thousands of England fans travelled to see their side lose the Ashes 5-0 and there were calls for him to be sacked when the English slumped to defeat in five of their first six One-day internationals.
But Fletcher has proved his detractors wrong after England ended their form slump by winning four games in a row to take the tri-series title from Australia.
''Duncan has taken quite a few knocks for this team,'' Flintoff told a news conference in Sydney.
''He has helped us in training. He has helped us in the nets and on the field and I hope we have repaid the faith he has had in us.'' Flintoff said Fletcher's coaching record was already beyond question but it was still important the tourists ended their disappointing tour of Australia on a high.
''He's been our coach for a long time and he's taken the side forward,'' Flintoff said. ''The improvement in this England side since he's been with us, a lot of that is down to Duncan Fletcher.
''Every player who has played under him has learnt something and taken something away to improve their game.
''On a long trip like this the coach has taken a few knocks...
he's taken flak on our behalf so to repay him like we have in the past few games and win a series and take some silverware home is great for the team but great for Duncan as well.'' England chairman of selectors David Graveney said the critics who had called for Fletcher's head should apologise.
''I hope they write letters of apology but that doesn't happen in the media world,'' Graveney told the BBC.
''I'm particularly pleased for the likes of Duncan Fletcher and Andrew Flintoff.
''It's part of the territory to come under the cosh but now they should sit back and bask in the sunlight.''