Characteristic behaviors of turbulent transition in the bottom boundary layer under irregular waves have been studied from laboratory data. It has been observed that flow transition under irregular waves is not only governed by instantaneous flow properties but also depends on the conditions in the preceding waves. While laminar-to-turbulent transition required a build-up of turbulent energy sufficient enough to produce traces of turbulence, for turbulent-to-laminar transition the turbulent wave was required to be followed by several successive smaller waves to allow total dissipation of turbulent energy. As a result waves with much higher Reynolds numbers show predominantly laminar properties, whereas, wave with Reynolds number as small as 5.0×103 shows turbulent behavior. Use of conventional wave friction factor diagram, therefore, becomes unsuited to indicate flow transition under irregular waves. Also transition takes place over a much wider range of wave Reynolds number than observed for regular waves.