Simons first attended Edgewater High School in Orlando, Florida, where during his sophomore year he averaged 17.8 points, 4.6 assists, 2.4 rebounds, and 1 steal per game in 30 games.[3] During his junior year he transferred to Montverde Academy in Montverde,[4] but after being a bench player, returned to Edgewater with the intention of holding his name back from college consideration for a year.[5] He graduated from Edgewater in 2017, averaging 23.8 points, 7.2 rebounds, 4.2 assists, 1.8 steals, and 0.5 blocks per game in 20 games played in his last year there.[3] Then, because of his reclassification in the Class of 2018, he attended the IMG Academy in Bradenton for a postgraduate year, although he had previously expressed interest in spending that year at the West Oaks Academy in Orlando instead.[6] During the summer of 2017, he also played for the United States men's national under-19 basketball team.[7]
On April 10, 2019, Simons had his first career start against the Sacramento Kings while the Trail Blazers rested Damian Lillard and CJ McCollum for the final game of the regular season. Simons put up career highs across the board with 37 points, 6 rebounds, and 9 assists, becoming the first Trail Blazers rookie to score 30-plus points since Lillard.
In the championship round of the Slam Dunk Contest during halftime of the 2021 NBA All-Star Game, Simons attempted to kiss the rim, but failed and still completed the dunk. Despite his failed attempt, he was named the 2021 Slam Dunk Champion on a 3–2 decision.[18]
On January 3, 2022, Simons scored a then career-high 43 points behind nine three-pointers, along with seven assists, in a 136–131 win over the Atlanta Hawks. In a postgame interview, he dedicated the game to his grandfather who died of cancer the previous night.[19] On March 28, he was ruled out for the remainder of the season with patellar tendinopathy in his left knee.[20]
On July 6, 2022, Simons re-signed with the Trail Blazers on a four-year, $100 million contract.[21][22] On October 21, Simons hit a game-winning floater in a 113–111 overtime win over the Phoenix Suns.[23] On December 3, Simons scored a career-high 45 points in a 116–111 win over the Utah Jazz.[24] On February 3, 2023, Simons scored 33 points in a 124–116 comeback win over the Washington Wizards.[25]
On October 25, 2023, Simons suffered a torn UCL in his right thumb against the Los Angeles Clippers, ruling him out for four to six weeks.[26]
Simons was given the name Anfernee due to his parents, Charles and Tameka, being fans of the Orlando Magic and naming him after former player Penny Hardaway.[27][28] Hardaway coached Simons during a Team USA Basketball training camp.[14]