Scotland international Iwelumo limped off during the first half of the Premier League newcomers' 1-0 victory over Perth Glory on Friday following a tangle of legs with former Leeds player Jacob Burns.
The 30-year-old was taken to hospital and manager Mick McCarthy confirmed afterwards that X-rays had revealed a break.
Iwelumo is now likely to miss Scotland's crucial World Cup qualifier in Norway on August 12 as well as well as the start of Wolves' campaign three days later.
The injury otherwise an otherwise positive outing for McCarthy's men at the Members Equity Stadium.
Sylvan Ebanks-Blake scored the only goal of a tight contest in the second minute.
Iwelumo flicked on a throw from George Elokobi to the lurking Ebanks-Blake, who took two attempts to slip it over the line in a goalmouth scramble.
Wolves' record signing Kevin Doyle played the second half but was a largely peripheral figure as fellow striker Andy Keogh shone, twice going within inches of scoring.