A number of different types of social interaction test have been used to delineate neural basis of social behavior. In most of previously reported testing paradigms, social sniffing time in unfamiliar testing environment is used as the only measurement of social interaction. Recently, we have established a new social interaction test paradigm which allow us to analyze not only social sniffing but also a number of other behaviors in home territory of experimental mice (Tsuda and Ogawa, PLoS One, 2012). By measuring social sniffing time and stretched approach to a stimulus mouse presented in a clear cylinder as well as moving distance and moving trace of experimental mice, we have successfully assessed levels of social investigation, anxiety, reactivity, and preference. In the present study, to further elaborate the paradigm we examined whether behavioral responses of experimental mice might be influenced by the levels of lighting intensity during behavioral tests which is known to affect emotional and anxiety-related behavior. Ovariectomized (OVX) female C57BL/6J mice were transferred to testing cage to establish their home territory 48 h before testing. They were tested for behavioral response to a cylinder containing an unfamiliar OVX female mouse for 15 minutes while the testing cage was illuminated either at 10, 25 (same as our previous studies), or 50 lux. We found that social sniffing time and time spent around the cylinder was shorter under 50 lux compared to 10 or 25 lux condition. On the other hand, lighting condition did not affect number of stretched approach and total moving distance in the test cage during exposure to stimulus mice. These results suggest that higher levels of illumination of the testing cage may inhibit social investigation toward unfamiliar females without affecting the levels of social anxiety and general activity.