He said the high esteem with which current Chelsea boss and ex-Baggies promotion-winning head coach, Roberto Di Matteo, and his assistant Eddie Newton still hold for the Black Country outfit also proved decisive.
"I'm really, very happy to be here - there are nice people around," the Belgium international told the WBA website.
"Since the first day I spoke to Chelsea about going out on loan, I've spoken to the gaffer here a lot.
"He was the first person who contacted me and that means a lot.
"He's been speaking to me every week since - even when I was in America with Chelsea - asking me about my situation.
"When you have a gaffer like that who has a desire to bring you to his club, as a young man, you feel confident to make the step into the unknown, because I don't know the Birmingham area that well.
"But I believe that will be good for my development as a young man and I'm very happy to be here.
"This club really convinced me a lot, also with the stadium and the fans."
Lukaku added: "I heard lots of positives about the club from Roberto Di Matteo and Eddie Newton.
"They really convinced me to come here.