Born in Makilala, Cotabato, he built his reputation as one of the fiercest and most exciting basketball warriors down south by joining in various competitions and leaving his marks on them.

[2] Having created a status in various collegiate and commercial leagues in Mindanao, Simon was easily handpicked to be a part of the Davao Eagles in the Metropolitan Basketball Association.

[10][11] Coming off the bench, he scored a new career-high 28 points as they outclassed Nueva Ecija Patriots during which he made five Blitz Three baskets in the game.

[16][17] At the end of the season, Simon's hard work and heroics on the court paid off as he was named as the Discovery Player of the Year.

In his first stint with the national team, PJ Simon scored 14 points to backup Reynel Hugnatan as the MBA All-Stars opened its 25th William Jones Cup campaign on a high note, tripping the much taller Russian club Lokomotive Novosibirsk, 78–68, at the Taipei Physical Education College Gym.

[21][22][23][24] Following the disbandment of the MBA in July 2002, Simon was immediately enlisted by Dazz Dishwashing Liquid, the Lamoiyan Corporation's Philippine Basketball League franchise.

In his first PBL finals appearance, PJ Simon led Dazz in a losing cause by scoring 18 points as they surrendered to the Welcoat Paintmasters in overtime in Game 1 at the Quezon Convention Center in Lucena City.

Hapee Toothpaste opened its championship run in the 2003 Sunkist PBL Unity Cup by defeating Viva Mineral Water behind the blazing guns of PJ Simon and Ryan Dy.

[36][37] In the 2003 PBL–CBF dual meet finals, he and Allan Salangsang combined for 35 points off the bench as they powered Fash Liquid to beat Grachiya Energy Boosters, 86–76, at the Cebu Coliseum.

[38][39] The following conference, PJ Simon edged out other illustrious cagers to bag the 2003–04 PBL Platinum Cup MVP with the print, radio, and TV media solidly rallying behind him.

But like his stints in the MBA and PBL, his PBA career did not start hot as he played behind fellow star rookie James Yap.

Owing to his impressive performance in the 2007–08 PBA Philippine Cup, he was selected in a reserve role to take part in the 2008 All-Star Game held in Bacolod City.

Simon did not disappoint the fans, as although he only played for 20 minutes, he scored 29 points on 11-of-14 field goals and 4-of-4 on the free-throw line to tow the South team in a thrilling victory in overtime over the North squad, 163–158.

Him and two-time MVP James Yap led the team to the quarterfinals,[76] in which the Llamados scored back-to-back wins against the Meralco Bolts.

In the Governors' Cup, they made a finals appearance and became the eventual champion, beating its sister team Petron Blaze Boosters in a tightly contested seven-game series.

Aside of him and the Mixers winning a rare Grand Slam in the 2013–14 season, he was a part of the PBA Second Mythical Team along with teammate Marc Pingris, Paul Lee, Sonny Thoss, and Rookie of the Year Greg Slaughter.

Along with close friend and Purefoods teammate James Yap, Simon guested at ABS-CBN's Pinoy Big Brother on April 23, 2008.