The goalkeeper will join the Hammers on a free transfer after his contract with the Blues expires in the summer, and is likely being brought in to provide competition to current number one Adrian.
Randolph, who has previously had spells with Charlton Athletic and Motherwell before his move to Birmingham in 2013, has been a consistent performer for the Blues and a mainstay in their side. He also has two caps for the Republic of Ireland.
West Ham were in need of a new number two after releasing previous incumbent Jussi Jaaskelainen earlier in the week, while they will also be looking to add numbers to their ranks in order to compete in Europe, having secured a Europa League place via the Fair Play League.
And that seems to be the stance many Hammers fans were taking, suggesting their new man will provide good back up for their current first-choice keeper and not much else.
Here is what some supporters have had to say on social networking site Twitter:
Happy to see a strong back up goalkeeper come in after losing Jussi. Welcome to Upton Park, Darren Randolph. #COYI— Dan Springate (@DCSpringate) May 30, 2015
Darren Randolph is signing today - and won't play a single minute next season.— West Ham Central (@WestHam_Central) May 29, 2015
West Ham have completed the signing off Darren Randolph, good back up keeper for Adrian! #whufc— Indonesia Hammers (@HammersIDN) May 30, 2015
Never heard of Randolph before. Hopefully he's a decent keeper that will play Europa League games. We basically need two squads.— West Ham COYI (@TheHammers_) May 30, 2015