In one of his cases, he represented some 8,700 steelworkers, shipyard workers, and manufacturers' employees in a consolidated-action asbestos poisoning suit that was partially settled in 1992.

The investigation went as far as executing a search warrant at one of his offices and federal prosecutors obtaining grand jury subpoenas, but Angelos was not charged with any related crimes.

[8] Angelos also represented the state of Maryland in a suit against Philip Morris and suing Wyeth, the makers of part of the diet pill combination fen-phen.

As of 2019, Angelos' law firm had offices in Baltimore, Towson, and Cumberland, Maryland; Philadelphia, Bethlehem, and Harrisburg, Pennsylvania; and Knoxville, Tennessee.

Though Angelos became known for demanding governmental oversight and fiscal responsibility, few of his calls for investigations into city agencies and spending led to lasting change.

[11] Angelos ran for the Democratic nomination in the 1967 Baltimore mayoral election, on the city's first racially integrated ticket, with Clarence Mitchell III was running for City Council President,[10] but he lost the nomination to D'Alesandro,[10] who received nearly 75% of the vote[12] and went on to beat Republican Arthur W. Sherwood in the general election.

[15] In 1993, Angelos assembled a group of investors to purchase the Baltimore Orioles of Major League Baseball (MLB) from New York venture capitalist Eli Jacobs.

While Angelos was the principal investor, contributing $40 million, his fellow Oriole group owners included novelist Tom Clancy, filmmaker Barry Levinson, and tennis player Pam Shriver.

On October 4, 1993, Jacobs sold the Orioles to Angelos' group for $173 million, the highest price paid for a sports franchise at that time.

Under Angelos' direction, the Orioles signed four high-priced free agents in 1994: Rafael Palmeiro, Sid Fernandez, Chris Sabo, and Lee Smith.

As his fellow owners mulled what action to take against Angelos — everything from a $250,000 fine for each game missed to forcing the sale of the Orioles — the lockout was finally settled in time for regular season play with major leaguers.

Subsequent investigations by MLB and the United States Department of Justice did not find evidence that the absence of Cuban players on the Orioles' roster or in its minor league system was due to discrimination.

In the early years of his ownership, Angelos was repeatedly criticized by The Baltimore Sun for the team's performance, but was praised by his associates for his work ethic and dedication.

[25] In November 2020, the league approved John P. Angelos, vice president of the Orioles and Peter's son, as the team's new control person.

[27] On January 30, 2024, Angelos agreed to sell the team to a group led by David Rubenstein that includes New York investor Michael Arougheti and Cal Ripken Jr. for $1.725 billion.

He donated millions of dollars to the Democratic Party and its candidates, and was a major supporter of the Greek Orthodox Cathedral of the Annunciation in Baltimore.