The 26-year-old defender, who twice won Brentford's player of the year gong, had entered into the final 12 months of his contract at Griffin Park and talks over a new deal hit an impasse.
Dean joins the 'Blues' on a three-year deal with the option of a further year for an undisclosed fee, becoming the club's tenth signing of the summer but Redknapp is not stopping there.
Despite being forced to withdraw from a move for Torino midfielder Afriyie Acquah, the former Tottenham boss is still hoping to boost his engine room before 23:00 BST on Thursday, with 'Sky Sports News' reporting that Birmingham have made a move for Sheffield Wednesday midfielder Barry Bannan.
Wednesday are not keen on selling the Scotland international, particularly so close to the deadline and are thought to have issued a hands off warning.
Scotland boss Gordon Strachan described the player as 'the best midfielder in the Championship' earlier this week, though it appears that he will be staying at Hillbrough for the time being.
OFFICIAL: We're delighted to announce the signing of Harlee Dean from Brentford for an undisclosed fee.
— Birmingham City FC (@BCFC) 30 August 2017
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