The influences of tide and water level rise on the cyclic medium-term seaward bar migration were examined using a one-dimensional numerical model of beach profile change, in which the cross-shore sediment transport rate was assumed to consist of four contributions due to sediment suspension and undertow, velocity skewness, velocity atiltness and beach slope. The model was calibrated with a year-long dataset of beach profiles obtained at the Hasaki coast of Japan in 1989, when the duration of medium-term seaward bar migration was approximately 1 year. The comparison between bar crest positions predicted with and without the tide at Hasaki during a two-year period including the calibration period of 1989 and the following year shows that the bar migrated further seaward without the tide than with the tide. The comparison between bar crest positions during the two-year period predicted with the tide and the water levels 0.5 m higher indicates that the bar crest positions were located further seaward with the higher water levels than with the tide in 1989. The difference between cyclic medium-term seaward bar migrations with and without the tide, and that with the tide and the higher water levels, are attributed to wave breaking on and seaward of the bar crests.