Town have confirmed that Hull City striker Aaron Mclean has also joined the Blues on loan until the end of the season.
Town boss Mick McCarthy has long been a fan of 29-year-old Mclean and tried to sign him from Peterborough when he was boss at Wolves.
Mclean, who had been set to join Millwall as recently as yesterday before the Blues matched the terms offered by the Lions, hasn't featured for the Tigers since the start of December and has scored three times this season. He is contracted until the summer of 2014.
The Hammersmith-born striker started his career with Leyton Orient, before dropping into non-league with Aldershot and then Grays, with whom he made his name. He joined Peterborough in 2006 and moved on to Hull in January 2011.
The signings of Mclean, who will wear the number 25 shirt while with the Blues, and McGoldrick would appear to suggest that DJ Campbell, whose loan spell from QPR ended earlier in the week, won't be returning to the club.
Town are yet to receive confirmation that the new signings are available for tomorrow's FA Cup tie at Aston Villa.