The president said the law will ensure "that everyone follows the same set of rules, so that firms compete on price and quality, not tricks and traps".
The law is a major victory for Mr Obama and the Democrats, who passed it with little Republican support after months of political wrangling.
It was vehemently opposed by the financial services industry.
The law tightens mortgage and consumer lending rules, improves disclosure for student borrowers and average investors and establishes a new consumer protection agency, among other provisions.
Almost every Congressional Republican opposed the bill, saying its new regulations would prove burdensome to businesses trying to create jobs.
The bill "fails to address the root causes of the kind of crisis it's meant to prevent", Senate Republican leader Mitch McConnell said last week.
"This is a bill that creates a vast new and unaccountable bureaucracy that, if past experience is any guide, will lead to countless burdensome, unintended consequences for individuals and small businesses, that will constrict credit and stifle growth in the middle of the worst economic period in memory."
But Mr Obama described the bill as a necessary measure to prevent future economic disaster, saying world's current economic troubles were caused in large part by "a breakdown in our financial system" and "a failure of responsibility from certain corners of Wall Street to the halls of power in Washington".