Importance of river rehabilitation has been emphasized since most flood plains were lost and rivers channelized. To prevent further biodiversity loss, it has been recommended that river channelization be completed with a method referred to as "tashizen" engineering (literally, rehabilitation with rich nature) in Japan. Such rehabilitation work generally aims at creating diverse microhabitat for fish by installation of pored-concrete blocks, boulders in wire cages, or planting riparian vegetation such as willows among numerous other methods. However, few elaborate studies to evaluate the effectiveness of such engineering work have been conducted. In the present study, we attempted to evaluate physical microhabitat variables and fish populations by comparing segments of rivers that had been rehabilitated by "tashizen" versus non-rehabilitated (i.e., channelized by regular engineering). A total of 19 streams were investigated in Aichi Prefecture and we found that microhabitats in the rehab segments were more diverse than the non-rehab; however, little difference was observed in the diversity of fish species and the population densities.