The 19-year-old forward signed a deal that will keep him at the club until the end of the 2027 season, with an option for an additional year.
The striker expressed excitement about beginning his European journey and hopes to enjoy a successful spell with the Finnish giants.
"It feels great to come here, this is a great opportunity for me. Striving towards domestic success and Euro competitions is exactly the kind of challenge I have been looking for. I can’t wait to help the team as best I can." Olorunfemi told club’s official website.
“I got a really good first impression of Helsinki. The food, weather and scenery are amazing. I look forward to settling here and getting to know more."
HJK reportedly beat competition from clubs in Sweden and Denmark to secure the signature of the promising youngster, who is regarded as one of Nigeria’s emerging talents.
Olorunfemi now joins the growing list of Tripple 44 Academy graduates making progress in Europe, alongside players like Ibrahim Adewale and Emmanuel Godwin.
HJK remain Finland’s most successful club, boasting 33 league titles, 14 Finnish Cups, and six League Cups.