Mustipher grew up in Owings Mills, Maryland and attended McDonogh High School.
[4] In Mustipher's sophomore year he took a step up after making 37 tackles, with 4.5 being for a loss, a sack, and a forced fumble.
[10][11] Mustipher had a breakout season in his extra year of eligibility after posting 37 tackles, 0.5 being for a loss.
[13][14] After not being selected in the 2023 NFL draft, Mustipher was signed by the Denver Broncos as an undrafted free agent.
[25] PJ, is the brother of former Chicago Bears, Baltimore Ravens and current Los Angeles Chargers center, Sam Mustipher.