The company went public Thursday, with shares rising more than 20 percent after pricing its initial public offering at $17. (Where's the stock now? Click here)
Buyout firm Thomas H. Lee Partners will still own a bit more than half of the company after the offering. THL bought Party City along with a consortium of investors in the summer of 2012.
CEO James Harrison said he was confident the company, which has most of its stores in strip malls, could prosper even as malls declined.
"Our category does sell online, but about 15 percent of what's in our stores really doesn't translate to online," Harrison said in a CNBC interview, adding that people would still seek out stores for things like balloons, cards and cheap candy.
Party City, which has more than 900 stores in the United States and Canada, said it would use the $372 million in proceeds mostly to pay down debt. More than 20 percent of its stores are franchised locations.
The company earned $56 million in 2014 on sales of $2.25 billion.