Mobile payments company Square started trading on the NYSE at $11.20 a share on Thursday. Shares closed at $13.07, up 45 percent from their trading debut.
A day earlier, the company had priced its initial public offering below the range it previously outlined.
Square priced its IPO at $9 per share after the bell Wednesday. Earlier this month, the company set the price range at $11 to $13 a share, valuing Square at up to $4.2 billion, or 30 percent less than in a private fundraising round a year ago.
Shares traded as high as 50 percent in the moments after the stock opened.
"It's all about getting the business and accelerating the business, and that's what we came here to do today and we did it," said CEO and co-founder Jack Dorsey in an exclusive interview on CNBC.
Dorsey is also the CEO of Twitter. He added that the focus will not be on trading Square's stock, but rather on growing the business.
Square's IPO is currently in the top 10 debuts this year of companies valued over $1 billion, even though it priced below its expected range.