The effect of thiourea (exposure to 0.05% solution) on the migratory activity of the climbing perch Anabas testudineus has been studied. It is established that thiourea simultaneously affects two components of the migratory behavior of climbing perch: rheoreaction and frequency of jumps out of water. Thiourea stimulates (by 27%) movement of specimens against the current and increases (by 31%) the frequency of jumps out of water. The effect of the substance is manifested on the fifth day of exposure, while specimens almost completely stop feeding on the twelfth day. Starvation caused by thiourea may play a crucial role in the effect of thiourea on the migratory activity of climbing perch.