The 23-year-old Salah-Eddine joined Roma in January 2025 for a reported fee of just over €8 million, but failed to secure a spot in the starting lineup in the Italian capital.
The Dutch youth international appeared in just three Serie A games for Roma last season, totalling 153 minutes along the way. Under new manager Gian Piero Gasperini, Salah-Eddine looks unlikely to gain playing time and was allowed to leave the club temporarily.
With PSV left-back Mauro Junior out with an injury, PSV were short-handed in the back line and looking for reinforcements. On Sunday, the reigning Eredivisie champions announced the signing of Salah-Eddine on a one-year loan deal.
"I am one hundred per cent fit and ready to get started as soon as possible," Salah-Eddine said on PSV's website.
"When PSV emerged as a serious option for me, I was immediately enthusiastic. After the first talks with the people at the club, I immediately felt a connection. After that, the decision was quickly made for me."
The left-footed defender is under contract at Roma until 2028.