Weak temperature dependence is reported for the Q-band magnetic circular dichroism of Cu phthalocyanine in an Ar matrix between 15 and 1.5 K. Moment analysis reveals a zero-field splitting of 1.5 +/- 0.5 cm(-1) in the singdoublet Q state. This is interpreted to be a consequence of interference between spin-orbit coupling and exchange interactions with the tripdoublet state.