TV stations were already required to compile data on how much political campaigns paid for advertisements, but the rule will require the stations to load that information into a database on the FCC's website.
For the first two years, the rule only applies to network-affiliated stations in the top 50 markets, but after that, all stations will have to comply with the requirements.
The FCC says the rule is part of its effort to put more information online, and watchdog groups hope the rule will shed light on the big money behind political ad campaigns by making the data more accessible. The 2012 election is expected to see an influx of spending from outside groups such as super-PACs.
Pelosi framed the rule as an effort to reverse the effects of the Supreme Court's decision in Citizens United, which loosened restrictions on outside spending in elections.
"With this small victory, we must keep moving ahead: to promote disclosure; to amend the Constitution and reverse the devastating effects of Supreme Court decisions that put special interests ahead of the public interest; to reform the system and empower the grassroots," she said. "We must ensure that the voices of the people determine the outcome of our elections, not the checkbooks of the few."
Republicans argue the FCC's regulation is an unnecessary and unfair burden on broadcast television stations.
Republicans pulled their provision to repeal the rule during a full Appropriations Committee markup on Wednesday. They offered instead two reporting requirements that would force the Government Accountability Office to analyze the economic impact of the rule.
Rep. Jo Ann Emerson (R-Mo.) admitted the FCC would likely implement the online database before the 2013 spending bill became law, making the attempt to defund the rule moot.
"A funding prohibition might not make any sense under these circumstances," she said.