Indoor air pollution dominates respiration exposure because people spend most of their time indoors. Generally, indoor PM2.5 concentrations are monitored at a fixed height in the breathing zone. However, the concentrations of PM2.5 likely vary vertically; thus, the vertical concentration profiles would help improve the understanding of indoor air pollution. Based on the basic principle of bistatic Lidar for boundary aerosol profiling, an indoor Lidar (I-Lidar) was developed to profile the vertical distribution of PM2.5 by imaging the PM2.5 scattering of a vertical laser beam onto a complementary metal oxide semiconductor (CMOS) camera. Unlike bistatic Lidar, the I-Lidar views the vertical laser beam perpendicularly from the side, which enables a high and relatively uniform vertical resolution throughout the profile. The images collected by I-Lidar were adjusted for transmission and scattering attenuation and calibrated against the measured PM2.5 concentrations using an array of PM2.5 sensors. The new device was tested in the field, and the measurements in a living room and kitchen of a rural household revealed the existence of vertical trends and dynamic change of PM2.5 concentrations. Potential applications of the device are discussed.