Federer, a four-time champion at the tournament for the world's top eight players, stretched his record to 11-0 against the seventh-ranked Spaniard, winning 6-1, 6-4 on the indoor hard court at the O2 Arena.
"I'm really happy the way I was able to get out of the first match here," said Federer, who will face Andy Murray on Tuesday in the round-robin tournament. "Starting off with a feisty top-10 player is never easy."
The fifth-ranked Murray defeated Robin Soderling 6-2, 6-4 in the early match.
Ferrer was playing at the ATP finals for the first time since losing to Federer in the 2007 final. And he looked nervous at the start, allowing Federer to break him in all three service games in the first set. The Spaniard's only winning game came on Federer's serve while already trailing 4-0.
"I served very bad through all the match," Ferrer said. "With Roger, it's impossible to take the chance if you [don't] serve good."
Despite the score, Federer didn't dominate. The 16-time Grand Slam champion was forced to deuce five times and had to save five break points in the second set.
"Looking at the score line, it doesn't reflect how tough it was," Federer said. "There were many close games, especially in the second set."
Federer's only break in the second set came at 2-2 when Ferrer sent a forehand wide and then raised his racket over his head before deciding not to smash it into the court.
In the crowd, the cheers were mostly for Federer -- unsurprising considering his six Wimbledon titles at the All England Club.
"He's the No. 2 of the world and the best player [in] history," Ferrer said. "Always when plays Federer, the people support more him than the other players."
Murray, who dropped one spot below No. 4 Soderling in last week's rankings, kept the ball from the Swede's strong forehand.
"I played very smart tennis today," Murray said. "And even when obviously it was getting tough in the second set, a lot of long rallies, I was on the defensive quite a lot, stuck to my tactics well and managed to come through."
Soderling, who again reached the French Open final this year and won the Paris Masters for the first time, had only five forehand winners while committing 12 unforced errors with his often dominating shot.
"He was defending really well," Soderling said. "I was hitting the ball pretty hard sometimes, try to be aggressive. Every time I came to the net, he came up with a really good shot."
Murray looked to be the more solid player throughout, facing only one break point while converting three of his six.
The Briton earned his first break early in the match, hitting a backhand winner off Soderling's serve to make it 2-1. He converted another to make it 5-2 and then served out the first set with a drop shot that hit the line.
"First set was not very good. I wasn't really there," Soderling said. "I think second set was better. But he played better than me today."
In the second set, the pair traded games until 3-3, when Murray broke again soon after taking a 0-40 lead in the seventh game.
"Second set I had to do a lot of running," Murray said. "Didn't always go for the lines. I hit a lot down to his feet, just made him play a lot of uncomfortable shots."
In doubles, top-ranked Bob and Mike Bryan of the United States defeated Jurgen Melzer of Austria and Philipp Petzschner of Germany 6-3, 7-5. Mariusz Fyrstenberg and Marcin Matkowski of Poland beat Lukas Dlouhy of the Czech Republic and Leander Paes of India 6-3, 7-6 (3).