Fans of the BBC One soap saw Windsor's character Peggy Mitchell tying the knot with Frank Butcher (Mike Reid) in a lilac gown ten years ago.
The outfit, which comes with matching shoes and handbag, is now expected to generate around £3,500 when it is sold by Valentine Auctions in Cosford, Shropshire on September 14.
Windsor's dress was originally put on sale at a This Morning charity auction in 2000 and has reportedly stayed with various private collectors since then.
Valentine Auctions' spokesman Peter Andrews told Express And Star: "Barbara Windsor has a huge fanbase, so the items are very special to many people.
"There are very few items of genuine EastEnders memorabilia other than a few photographs so the wedding outfit, which includes an authentic signed card from the actress, is extremely rare.
"It is bound to attract a great deal of interest from collectors and fans of the TV series."
Peggy and Frank split on screen in 2000. Mike Reid went on to make a number of guest appearances on the programme before passing away in July 2007.
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