Born in
Rotterdam, Wim van der Gaag played in his youth in the now-defunct RFC Rotterdam. In 1954 he turned professional in the short-lived
NBVB league, scoring the second goal of
BVC Rotterdam on 7 November 1954, in a game that ended in a 3–2 loss against
BVC Den Haag. In 1954–55 Van der Gaag played for
SBV Vitesse, scoring two goals that season. In 1955–56, at
SC Emma, he was the top scorer with
Janus van der Gijp, both scoring seven goals. In 1957?–59?, Van der Gaag played at
BVV in the
Eredivisie. Late August 1959, Van der Gaag scored the first two goals in BVV's 4–0 victory over
SBV Excelsior. He continued to the Australian sides Sydney Austral,
Sydney FC Prague,
Pan Hellenic Sydney,
South Coast United (1961–62), and
Ringwood Wilhelmina. Back in the Netherlands, at
AGOVV Apeldoorn (1966–67), Van der Gaag was instrumental in its 2–0 victory against
Excelsior Rotterdam on 14 August 1966, this time scoring only one of two goals. At PEC Zwolle (1967–68), he scored both goals in its 2–1 national cup victory against
Zwolsche Boys on 31 December 1967. The victory was especially sweet as it was against PEC's urban rival. ==Managerial career==