De Palmer enjoyed most of his tennis success while playing doubles. During his career, he won six tour doubles titles and finished runner-up an additional six times. He achieved a career-high doubles ranking of world No. 20 in 1986.
DePalmer had a career high singles ranking of 35, with wins over Jimmy Connors, Vitas Gerulaitis, Mel Purcell, Peter Fleming, Peter Lundgren, Paul McNamee, Jakob Hlasek, and Tim Gullickson. He reached the singles final in Ancona, Italy, in 1982, losing to Anders Jarryd 6-3, 6-2.
DePalmer coached Boris Becker for several years, as well as other professionals.
Grand Prix and WCT finals
Doubles: 12 (6 titles, 6 runner-ups)
|Loss||1.||1984||San Francisco, U.S.||Hard (i)||Sammy Giammalva Jr.|| Peter Fleming
|Win||1.||1985||Livingston, U.S.||Hard||Peter Doohan|| Eddie Edwards
|Loss||2.||1985||Stockholm, Sweden||Hard (i)||Gary Donnelly|| Guy Forget
|Win||2.||1985||Vienna, Austria||Carpet (i)||Gary Donnelly|| Sergio Casal
|Loss||3.||1986||Florence, Italy||Clay||Gary Donnelly|| Sergio Casal
|Loss||4.||1986||San Francisco, U.S.||Hard (i)||Gary Donnelly|| Peter Fleming
|Win||3.||1986||Tokyo Indoor, Japan||Carpet (i)||Gary Donnelly|| Andrés Gómez
|Win||4.||1986||Hong Kong, U.K.||Hard||Gary Donnelly|| Pat Cash
|7–6, 6–7, 7–5|
|Win||5.||1986||Johannesburg, South Africa||Hard (i)||Christo van Rensburg|| Andrés Gómez
|3–6, 6–2, 7–6|
|Loss||5.||1987||Chicago, U.S.||Carpet (i)||Gary Donnelly|| Paul Annacone
Christo van Rensburg
|Win||6.||1989||Florence, Italy||Clay||Blaine Willenborg|| Pietro Pennisi
|4–6, 6–4, 6–4|
|Loss||6.||1989||Bristol, England||Grass||Gary Donnelly|| Paul Chamberlin