Baroni grew up in Massapequa Park on Long Island, New York. He attended Massapequa High School where he was on the wrestling team, but was expelled when he was a senior for assaulting a janitor at the school, only a week before the state wrestling championships in which he was ranked first. Baroni attended Nassau Community College and became a two time All-American wrestler there, placing fifth and second in the nation. Baroni then attended Hofstra University before transferring to Central Michigan University, where he was a double major in biology and psychology, and lived in Deerfield E14. He was also an amateur bodybuilder from the age of 17 to 20, competing in six shows in which he placed either first or second. He studied kickboxing under Keith Trimble, and had seven matches, winning all by knockout. He also competed in 10 amateur boxing matches, also winning all 10 by knockout.
Baroni debuted in the UFC in only his second professional fight, at UFC 30 in Atlantic City, New Jersey. The bout was against fellow striking specialist Curtis Stout, and Baroni won by unanimous decision. Baroni was an undefeated 3-0 before getting his second fight with the UFC at UFC 34 against Matt Lindland, whom Baroni would develop a rivalry with later in their careers. Baroni lost the fight by decision, and was handed his first professional loss. However, Baroni would then quickly make a name for himself in the UFC with several impressive stoppage victories. His signature win was a decisive KO victory over former UFC Middleweight Champion Dave Menne on September 27, 2002. Baroni famously jumped on the top of the cage and proclaimed himself to be the "best eva" after the knockout of Menne.
Baroni then rematched Matt Lindland to whom he had previously lost to by judges' decision. In their rematch, Baroni suffered a second loss to Lindland by another judges' decision. He was then matched up against a teammate of Matt Lindland, future UFC Middleweight Champion Evan Tanner at UFC 45 – Revolution. Baroni dominated the beginning of the match against Tanner, but when the fight was stopped to check a cut on Tanner, Tanner regained his composure and the momentum turned, leading to the referee stopping the fight due to Baroni taking several undefended strikes on the ground. This decision was controversial as the referee Larry Landless had asked Baroni if he wanted to quit. Baroni said he believed he was asked if he wanted to continue, and said "yes". Landless stopped the bout, and was struck by a furious Baroni. Baroni was subsequently suspended for 4 months for striking the official. Upon his return Baroni got a rematch with Tanner at UFC 48 – Payback but went on to lose via decision.
Despite losing three fights in a row, the UFC matched Baroni against the relatively unknown Pete Sell. Following training with Enson Inoue, Baroni dominated early on with numerous takedowns and a dominant standup, however, Sell secured a guillotine choke and Baroni appeared to lose consciousness, but then tapped out for the first time in his career thereby ending the fight.
Baroni joined Hammer House soon thereafter and rebounded in Japan's PRIDE Fighting Championships promotion with several knockout victories against Ikuhisa Minowa, Ryo Chonan, and Yuki Kondo. On June 4, 2006, Baroni was summarily defeated by Ikuhisa Minowa, whom he had developed a rivalry with, via unanimous decision in the Bushido Welterweight Grand Prix 183 lb (83 kg) tournament in 2005.
On October 21, 2006 Baroni captured a victory over boxer turned mixed martial artist Yosuke Nishijima via kimura in the first round at PRIDE 32, PRIDE's first American show. In the post-fight interview Baroni humorously admitted that he did not know the name of the hold he applied and only saw it on television a couple days before the fight.
Frank Shamrock and Baroni had engaged in a war of words following Shamrock's fight with Renzo Gracie. The two faced off at Strikeforce Shamrock vs. Baroni, a co-promotion between EliteXC and Strikeforce on June 22, 2007 on Pay-Per-View. Shamrock defeated Baroni, knocking him down with punches in the first round and finishing him off with a rear naked choke in the second round. It was ruled a technical submission victory for Shamrock as Baroni was choked unconscious before he could tap. Baroni stated many times that he was not going to tap anyway.
Following the Shamrock fight, the California State Athletic Commission announced that Baroni tested positive for two types of anabolic steroids, boldenone and stanozolol. Baroni appealed the $2500 fine and faced a one-year suspension. Ultimately, the fine was upheld although the suspension was reduced to six months.
Baroni had asked that the remaining urine from the test conducted by Quest be sent to the Carlson Company, a laboratory located in Colorado Springs, Colorado. While it did not appear among the 40 facilities recommended by the CSAC, Carlson appealed to the fighter as a rare lab that tested for both DNA and steroids.
There was not enough of a sample for the lab to determine the identity of its owner, though Carlson apparently had enough to determine the sample they received from Quest did not contain boldenone or stanozolol.
Baroni faced Hawaii's Kala Hose on March 15, 2008 for the vacant ICON Sport Middleweight title. Former champion Robbie Lawler was stripped of the title due to his inability to defend it on numerous occasions. While Baroni came out strong during the first round of the fight, his stamina began to fade and Hose started to dominate the fight. Hose ultimately defeated Baroni by TKO early in the fifth round to become the new ICON Sport Middleweight Champion.
Baroni fought Joey Villasenor in the first ever live network television broadcast of MMA on CBS. In the beginning of the fight Baroni caught Villasenor's high kick which brought him down to the mat, where Baroni threw punches from guard. Baroni then let Villasenor stand up, Baroni then got struck a few times and was put into a guillotine choke. Villasenor then let go of the choke and started delivering unanswered punches that dazed Baroni, prompting the referee to stop the fight at the 1:11 mark of the opening round. This was Baroni's second consecutive TKO loss.
Baroni made his Cage Rage and Welterweight debut at Cage Rage 27 on July 12, 2008, against British fighter Scott Jansen. He began the fight with a takedown, and came close to finishing the fight with an armbar with which he appeared to hyper-extend Jansen's arm. Following a standup call from the referee, the two fighters exchanged blows, Baroni throwing a right to the body, followed by a right-handed punch which to Jansen's chin. Jansen dropped, his head bouncing off the floor.
Baroni went to check on Jansen and was attacked by Jansen's brother who had made his way into the cage with the cornermen.
In his second appearance in the promotion, he lost to Joe Riggs at Strikeforce: Lawler vs. Shields on June 6, 2009 in St. Louis, Missouri at Scottrade Center.
In late 2009 Baroni returned to once again fight in the UFC. He signed a multi-fight deal & his return fight was at UFC 106 on November 21, 2009 against TUF 7 winner Amir Sadollah. Sadollah defeated Baroni by unanimous decision.
After a decision loss to Sadollah, Phil Baroni spent 2 months in Phuket, Thailand learning Muay Thai at Tiger Muay Thai (TMT) with legendary coach Kru Yod. He practiced kicks, knees and elbows to improve his striking game. He also celebrated his 34th birthday in Phuket. The TMT crew posted videos of Baroni's workouts, showing how the training sessions improved Baroni's stand up technique, and work with nutritionist/strength & conditioning coach brought Baroni back to incredibly good shape in two months.
Baroni stated his intentions to return to the Middleweight division.
Baroni was scheduled to face John Salter on August 28, 2010 at UFC 118, however he was forced off the card with an injury.
Baroni next fought TUF 11 alumni, Brad Tavares at UFC 125. After dropping Tavares with a left hook early, Baroni was caught with a high kick in the later part of the round with Tavares eventually securing the TKO victory. At the post-fight interview with Ariel Helwani, Baroni said that he is expecting to be cut from UFC, but he refuses to quit. Baroni was then subsequently released.
He held a UFC record of 3–7.
After his UFC release, less than two weeks later, Baroni signed a new multi-fight contract with Titan Fighting Championships. He fought at Titan Fighting Championships 17 against Nick Nolte. He won the fight via unanimous decision.
Baroni returned from shoulder surgery against local favorite Chris Holland on June 2, 2012 at Ring of Fire 43: Bad Blood. Baroni dominated Holland in the first round, taking Holland down multiple times and landing heavy punches that opened a gash above Holland's left eyebrow. Baroni was visibly tired heading into the second round and was rocked by multiple hooks from Holland, Baroni ended up losing via TKO due punches in the second round.
On July 18 it was announced that Baroni would be facing Yoshiyuki Yoshida at ONE Fighting Championship: Champion vs. Champion at the Singapore Indoor Stadium on September 3. Baroni lost the fight via unanimous decision. After the fight Baroni had surgery on a shoulder injury which had affected him since college.
Baroni was scheduled to face Roger Huerta at ONE FC: Destiny of Warriors on June 23 but he was pulled from the fight after his TKO loss to Chris Holland on June 2.
On August 31, 2012 Baroni faced Rodrigo Ribeiro at ONE FC: Pride of a Nation. Baroni stunned Ribeiro with the first punch he threw, Baroni chased a wobbly Ribeiro landing heavy punches as the Brazilian retreated; Baroni then knocked Ribeiro down with a punch combination and finished the fight due to soccer kicks and punches just sixty seconds into round one. Baroni became the first man to ever knock out Ribeiro, the 60-second victory marks Baroni's first knockout win in over four years.
Baroni represented ONE FC in a fighter-sharing program at Dream 18 on December 31, 2012 against Hayato Sakurai. He lost the fight via unanimous decision.
Baroni next appeared on the ONE FC 9: Rise to Power card against Nobutatsu Suzuki. He lost the fight due to an ankle injury.
It was announced on March 13, 2014 that Baroni had signed a deal with Bellator MMA, and was expected to make his debut against Jesus Martinez on May 2, 2014. However, Baroni was forced out of the bout due to injury and was replaced by Ryan Contaldi.
Baroni faced Karo Parisyan in his debut fight at Bellator 122 on July 25, 2014. He lost the fight via TKO in the first round and was subsequently released from the promotion.
Since April 2009, Baroni has occasionally worked as an MMA commentator for the MMA Big Show fight organization, Tachi Palace Fights, and India's Super Fight League.
In 2014 Baroni is training to become a professional wrestler at D'Lo Brown Pro Wrestling Academy.
On March 18, 2016 Baroni was announced to wrestle at Pro Wrestling Syndicate Super Card 2016 against former ECW superstar New Jack on June 11 at Starland Ballroom in Sayreville, New Jersey.
Baroni and his girlfriend were married on October 12, 2008. Baroni was formerly represented for years by MMA agent Ken Pavia but after his move to American Kickboxing Academy Baroni's been managed by Bob Cook and DeWayne Zinkin of Zinkin Entertainment and Sports Management. Phil is now managed by pro mma fighter and professional wrestler Matt "The Granimal" Granahan's the American Combat Association since his move to professional wrestling along with other UFC stars turned pro wrestlers Kamal Shalorus and Dan Severn Before becoming a professional fighter, Baroni worked various jobs including construction, delivering pizzas, bouncing and a car salesman.