Abstract Background Since lymphocytes predominantly express delayed rectifier K+-channels (Kv1.3) that trigger lymphocyte activation, statins, which exert immunosuppressive effects, would affect the channel currents. Methods Employing the patch-clamp technique in murine thymocytes, we examined the effects of statins on Kv1.3-channel currents and the membrane capacitance (Cm). Results Pravastatin significantly suppressed the pulse-end currents of the channels. Lovastatin and simvastatin also suppressed the peak currents, significantly decreasing the Cm. Conclusions This study demonstrated for the first time that statins inhibit thymocyte Kv1.3-channels. The slow inactivation patterns induced by lovastatin and simvastatin may be associated with their accumulation in the plasma membranes.