We search for CP violation in the decay D+ → K S0K+ using a data sample with an integrated luminosity of 977 fb-1 collected with the Belle detector at the KEKB e+ e- asymmetric-energy collider. No CP violation has been observed and the CP asymmetry in D+ → KS0K+ decay is measured to be (-0.25±0.28±0. 14)%, which is the most sensitive measurement to date. After subtracting CP violation due to K0-K̄0 mixing, the CP asymmetry in D+ → K̄0K+ decay is found to be (+0.08±0.28±0.14)%. © 2013 SISSA.