In the 1999 summer, Mols signed for Scottish side Rangers, scoring nine times in his first nine Scottish Premier League matches. However, during a UEFA Champions League clash against Bayern Munich, he collided with opposing goalkeeper Oliver Kahn, which resulted in a serious knee injury[1] – in the same competition, he previously helped his club crush PSV Eindhoven 4–1 at home by scoring twice, whilst in the league, he put four past former Ranger Andy Goram's Motherwell.[2][3]
Mols made his return from the injury on 9 September 2000 in a league game against Dundee.[4] In the following years, Mols endured a tough rehabilitation process,[5][6] eventually recovering fully and scoring 13 times in 27 matches during the 2002–03 championship-winning season, which earned him a one-year extension in his contract.[7] In December 2002, he notably scored the winner in the Old Firm contest against Celtic (3–2),[8] and left club and country in June 2004, having collected a total of five trophies. He got sent off on his final appearance for Rangers against Dunfermline.[9]