The 26-year-old midfielder made the emotional decision to leave Arsenal last month after he was told by new Gunners coach Unai Emery that he was no longer in the Club’s plan.
After sealing the deal and passing his medicals, Wilshere told the club’s website: ‘It feels good, it feels special.’
‘Many people know that I’ve had a special bond with this club growing up.
‘People will have seen the picture of me in a West Ham shirt and I’ve got good memories of my childhood supporting West Ham, watching them at Upton Park. It feels good and of course my family and a few of my friends are West Ham fans so everyone’s buzzing.’