President Trump’s family business sued Capital One on Friday for “unjustifiably terminating” more than 300 of its bank accounts after the Jan. 6, 2021, attack on the Capitol, the latest sign that the president and his allies are seeking retribution against those who once shunned them.

In a complaint filed in state court in Florida, the Trump Organization accused the bank of arbitrarily closing its accounts in June 2021 in violation of various consumer protection laws. The accounts held millions of dollars at the time, according to the lawsuit.

“By filing this lawsuit, we seek to hold Capital One accountable for the millions of dollars in damages they caused, not just to our company, but to the many dozens of properties, hundreds of tenants and thousands of Trump Organization employees who relied on these accounts for their livelihoods,” the company said in a statement.

The bank, one of the largest financial institutions in the United States, did not provide a reason at the time for closing the accounts, the lawsuit said.

But in the aftermath of Jan. 6, when Mr. Trump’s supporters stormed the Capitol, a number of financial institutions cut ties with his family’s real estate business. The group’s lawsuit against Capital One could portend similar actions against other banks.

“More to come,” Eric Trump, one of the plaintiffs and the leader of the Trump Organization, said in a statement on Friday.

The legal action coincides with his father’s broader campaign to exact revenge on perceived enemies. Since taking office, the president has revoked the security details of high-profile critics and taken aim at a law firm representing Jack Smith, the special counsel who investigated him.

The lawsuit against Capital One also underscores the Trump Organization’s newly emboldened posture now that its owner has reclaimed the White House. After years of shedding properties and halting expansion amid political and legal tumult — including a tax fraud conviction in New York — the company has struck a number of new hotel deals in the past year.

Many of the deals are based in countries central to U.S. foreign policy, raising potential conflicts for Mr. Trump’s administration.

The president’s family business suing a bank that is regulated by his administration could also pose an array of conflicts of interest. Capital One is seeking approval from federal banking regulators for its proposed merger with Discover Financial Services. And the Trump administration last month dropped a lawsuit that accused Capital One of cheating customers out of $2 billion in interest payments on their savings accounts.

The new lawsuit from the Trump Organization might also pose issues for the company. If it continues to expand, it might seek loans from major financial institutions. That prospect, however, has not stopped the company from settling a score with one of its longtime banks, which maintained accounts for the group and the Trump family.

“Capital One’s unilateral decision came about as a result of political and social motivations and Capital One’s unsubstantiated, ‘woke’ beliefs that it needed to distance itself from President Trump and his conservative political views,” the lawsuit said. “In essence, Capital One ‘de-banked’ plaintiffs’ accounts because Capital One believed that the political tide at the moment favored doing so.”

The lawsuit accused the bank of “unlawful, deceptive and reckless conduct,” citing supposed violations of consumer protection laws in several states, including New Jersey and North Carolina. The Trump Organization is largely based in Florida.

In a statement, a spokesman for Capital One denied the accusations, saying the bank “has not and does not close customer accounts for political reasons.”