The 28-year-old left-back trained with his new team-mates this morning and goes straight into the squad for the clash with Birmingham City at St Andrew's.
Albion head coach Oscar Garcia said, “From the first day that we arrived here we knew that we needed a left-back. Now we have Stephen and we think he can help us a lot.
“He can also play as a winger, and we are happy that Stephen has joined us.
“He is fit enough to play and will be available on Saturday.”
Ward began his career at Bohemians in his native Ireland, before joining Wolves in 2007. He has made over 230 appearances for the midlands club – scoring nine times - and was a key part of the side that won promotion into the Premier League in 2009.
The versatile defender, who has also tried his hand in midfield and attack during his career, made his international debut in May 2011.
Later that year he scored in the second leg of the Republic’s play-off with Estonia for Euro 2012 qualification, and was part of Giovanni Trapattoni’s squad the following year in Poland & Ukraine.