Machida (21-4) controlled distance and rocked Mousasi with several hard left head kicks en route to the win. Judges scored the bout 50-45, 50-45 and 49-46.
"I obviously would like to get the champ," Machida said. "It's up to the UFC. President [Dana White] has to decide who I'll get."
The main event contest in Jaragua do Sol, Brazil, did not provide the highlight-reel finish of Machida's UFC 185-pound debut in October, when he knocked out Mark Munoz just 3 minutes into the first round -- but it was nearly as impressive.
The former UFC light heavyweight champ got off to a somewhat cautious start, but seemed to pick things up as each round progressed.
He broke the ice in the opening frame with a left kick to the body and had Mousasi visibly frustrated midway in the second with his ability to circle away from exchanges.
The Brazilian crowd erupted in the second round when Machida landed one of the biggest strikes of the fight, a high left head kick. Mousasi (34-4-2) appeared undeterred, however, and answered moments later with a combination.
"He's a great fighter, he's a real champ," Machida said. "I wanted to finish it in another way, but I was able to get the points."
Just when it appeared Mousasi was starting to find his range, Machida switched his approach and had him confused again. He landed a spinning back kick in the third round and opened a cut on the bridge of Mousasi's nose during an exchange.
Machida's corner told him he was well ahead after the third round, which appeared to have an effect on his strategy in the fourth. He spent a long period circling away from Mousasi, before executing a trip in the center of the cage.
With just seconds remaining in that round, Mousasi landed an illegal upkick from his back while Machida had a knee on the canvas. Referee Mario Yamasaki paused the bout, but did not take away a point from Mousasi.
Machida actually came out more aggressive in the fifth, even taking Mousasi's back in the final minute. He landed one last right hand as the bell ended what was a tense, but relatively one-sided affair.
Machida entered the contest as the No. 4-ranked middleweight in the world, according to ESPN.com. He is attempting to become the third fighter in UFC history to win a title in multiple weight classes, joining BJ Penn and Randy Couture.
Souza outgrapples Carmont
With the fight on the line in the final round, Souza (20-4) dominated Carmont on the floor to earn a unanimous decision and move one step closer to the UFC title. Judges scored the 185-pound contest 29-28, 29-28 and 30-27.
"I was expecting a tough fight; I was ready to fight for three rounds and that's what happened," Souza said. "I thought I was going to submit him a few times, but he was able to defend my attempts."
After an initial feeling-out process, Souza scored the first move of the fight when he took Carmont down and jumped immediately to his back following an exchange on the feet.
With the Brazilian crowd behind him, Souza nearly locked in the rear-naked choke after slipping his left arm under Carmont's chin, but the French middleweight found a way to survive.
Carmont (22-8) refused to fold after the first round and actually carried a lot of confidence into the middle frame. He defended several Souza takedowns and started to find range with his right hand. He rocked Souza at one point with a counter right hand and followed it up moments later with a hard 1-2 combination up the middle.
Both corners urged their fighter to pick it up in the deciding third round, and it was Souza who responded. One minute in, he landed a key takedown, which Carmont would never recover from. Souza eventually took his back, but couldn't secure a finish before time ran out.
I'm in a good place in the division, but if they feel I need to fight again before I get a chance at the belt, it's not a problem," Souza said. "Getting the title would be a dream come true."
A former Strikeforce middleweight champion, Souza remains perfect in the UFC at 3-0. He recorded three first-round finishes in 2013, two of which occurred in the Octagon. Carmont suffers his first loss since April 2008.
Silva bombs out Sato
Erick Silva has a habit of following heartbreaking losses with spectacular wins.
Silva (16-4) required less than one minute to dispose of UFC newcomer Takenori Sato, earning a first-round TKO victory just 52 seconds into the welterweight bout.
It's the third time in Silva's UFC career he has followed a loss with a first-round win.
Sato (17-9-7) looked overmatched from the start. He visibly winced after eating an early Silva leg kick, which prompted him to shoot on a single-leg takedown.
Silva never came close to falling to his back. In fact, the Brazilian actually hopped into the air and tried to heel Sato as he clung to his other leg. After resecuring his balance, Silva started to unload punches to the side of Sato's head.
Yamasaki warned Sato to keep moving, but the Japanese fighter slumped and the fight was quickly called.
"I needed a win, but at no point felt pressured," Silva said. "Losing my last fight served as motivation, not as pressure.
"I trained very hard, it was the best camp of my life. I was the first to arrive in the gym and the last one to leave. I was very hungry for the win."
Silva improves to 4-3 since signing with the UFC in 2011. He suffered a one-punch knockout loss to Dong Hyun Kim in his last fight, at UFC Fight Night 29 in October.
Musoke recovers to outlast Andrade
It's hard to say definitively whether a premature celebration cost Viscardi Andrade a win or not -- but it certainly might have.
Nicholas Musoke (12-2) improved to 2-0 in the UFC with a unanimous decision win over Andrade (17-6). All three judges scored the welterweight bout 29-28.
Midway through the first round, Andrade dropped Musoke with a looping overhand right. Musoke temporarily went limp as he fell to the ground, which prompted Andrade to raise his arms in celebration.
Musoke, however, was quick to recover, which referee Keith Peterson recognized. Andrade did not waste a lot of time following him to the ground, but the Brazilian is likely to second-guess that moment of hesitation following the loss.
Musoke evened the scorecards in the second round. He rocked Andrade on the feet with a left head kick and right hand. Eventually, he took the fight to the floor, where he scored points with hammerfists from Andrade's guard.
Andrade looked tired in the final round and Musoke took advantage, pinning him up against the fence before working for a takedown. The Swedish fighter ended up taking Andrade's back, where he finished the round.
Afterward, Andrade tried to explain what went wrong in Round 1, and dismissed the notion that he faded in Rounds 2 and 3.
"The moment I hit him, he rolled his eyes and stopped, so I lifted my arms [in celebration]," Andrade said. "Then he moved, the referee told us to continue and it was too late.
"He recovered very well. I hit him with hard punches, a few of which rocked him, but he managed to push through and impose his game. I was well-trained, that wasn't the problem."
A former contestant on "The Ultimate Fighter: Brazil," Andrade sees a seven-fight win streak snapped. Musoke extends his current win streak to three.
Oliveira notches another submission win
It was only a matter of time before Charles Oliveira got back on track at 145 pounds.
Oliveira (17-4) ended a two-fight losing streak with a submission win over Andy Ogle in the third round. It was his first victory since June 2012.
The Brazilian dominated the entirety of the featherweight bout, although Ogle (9-4) showed heart along the way. The finish eventually came via triangle-choke at 2:40 of the final round.
"My goal today was a knockout, but I saw he was getting the better end of it standing up," Oliveira said. "I practice my jiu-jitsu a lot and I tried to use it to the best of my abilities.
"He was very slippery and defended many submission attempts very well, but thankfully I was able to get the win."
Oliveira took advantage of his superior grappling game immediately, taking Ogle down and working to his back. He spent nearly all of the first round on Ogle's back with a body triangle, but couldn't find a finish.
Ogle looked better after the first round, as he held his own in scrambles and worked into top position several times. It was never for very long though, with Oliveira utilizing sweeps or submission attempts to get off his back.
In the last round, Ogle came out swinging, looking for a knockout. Oliveira threw a counter jab that scored the fight's only knock down. Ogle responded well and continued to move forward, but couldn't escape the late choke.
Oliveira, 24, scores his fifth UFC win, all of which have come via submission. Ogle drops to 1-3 since joining the promotion in 2012.