Aldo used a crisp jab and his trademark powerful low kicks, not to mention impressive takedown defence, to outpoint Edgar in a rousing five-round affair.
"It was a great fight and I knew I had to work step by step and round by round to get the victory," Aldo said. "He was trying to take me down, so I stopped it with my kicking."
Aldo (22-1) started out in dominant fashion, snapping Edgar's head back with straight punches and staggering him with thudding low kicks. Fighting for the first time at 145 pounds, Edgar (15-4-1) looked quick and aggressive, but he was simply unable to track down the champion, who remained at a distance and picked his shots on the outside.
That pattern continued through the first three rounds, but things took a definitive change in the fourth.
Edgar, widely respected for his never-ending gas tank and admirable heart, proved again the championship rounds are often his best as he became the aggressor and landed several crisp punches and a series of his own low kicks. They didn't land with the same authority as Aldo's, but still brought the crowd to life with the possibility of an upset.
In the fifth round, Edgar again pushed forward and looked to tag the champion at every available opportunity, but Aldo showed masterful use of range and timing as he avoided taking any serious damage.
In the end, Aldo won a unanimous decision with scores of 49-46, 49-46 and 48-47 with Edgar taking only the fourth on two of the judges' cards with a third also giving him the final frame.
Aldo's next challenger is unclear, but UFC president Dana White revealed top UFC lightweight Anthony Pettis asked for an opportunity to drop to 145 pounds and challenge for the belt.
In the night's co-feature, Antonio Rogerio Nogueira (21-5) returned from a 14-month layoff to score an upset win over former UFC light heavyweight champion Rashad Evans (17-3-1).
In what proved a somewhat lacklustre affair, Evans appeared hesitant to engage and never took advantage of his expected speed and wrestling advantage. Instead, he settled for pawing a jab on the outside, which southpaw Nogueira simply blocked with his right hand before firing straight lefts down the middle.
The slow-paced fight drew the ire of the audience throughout the 15-minute affair, but Nogueira methodically racked up points by remaining the busier fighter over the final two rounds and claimed a unanimous-decision win, 29-28 on all three judges' cards.
"I think that this is is one of my biggest victories because Rashad Evans is a big champion and he's very tough," Nogueira said after the fight.
"I didn't want to talk a lot in the lead up to the fight. I just trained very hard and I came with good boxing and great wrestling and I was able to make it hard for him to take me down."
Evans had been considered as a potential opponent for UFC middleweight champion Anderson Silva, but the poor performance eliminated any potential demand for that matchup.
Additionally, Brazilian underdog Antonio (Bigfoot) Silva (18-4) earned an emotional third-round TKO over the man who was fighting for a shot at the UFC heavyweight title, Alistair Overeem (36-12).
Overeem started the bout by smiling at his opponent and moving forward with his hands down and showing a complete lack of concern for his opponent's striking attacks. However, the Dutch striker never really offered an obvious gameplan other than to move into the clinch and look for knees to the body.
Silva struggled to find room to strike, but he also absorbed little damage through the opening 10 minutes of the fight.
In the third, everything changed.
Despite losing the first two rounds, Silva looked energized and shucked off an early takedown attempt from his opponent only to explode with a series of counter punches. A right hand scored flush, and Overeem wobbled to the cage and looked to cover up.
Sensing his opportunity, Silva unleashed a flurry of straight shots to the jaw and Overeem slumped to the canvas. Referee Herb Dean waved off the fight 25 seconds into the final round, and Silva stood over his opponent and yelled once again at the man who earlier in the week had promised to "destroy" him.
"It really bothered me that he hadn't respected me in interviews leading up to the fight," Silva said after the win. "He talked a lot of trash, and I told him that I'd make him respect me tonight."
Overeem was expected to receive a title shot against UFC heavyweight champion Cain Velasquez with a win. White revealed at the evening's post-event press conference that Silva may now take that slot instead.