To explore the influence of tidal events on protozoan periphyton fauna along tidelines, a 1-month baseline survey for bioassessment was conducted in an intertidal zone of the Yellow Sea, Northern China. A total of 27 protozoans species were identified among five sampling sites along five tidelines (sites A–E). The periphytic protozoans showed a significant variation in species distribution and community pattern along five tidelines. Species richness decreased from the high tideline (site A) and reached the minimum value at the middle tideline (site C), followed by an increase up to the low tideline (site E). Individual abundances peaked at site C and leveled off at the other four tidelines. Species richness, evenness, and diversity showed low value at site C compared with those at the other four sites. These findings suggest that periphytic protozoan fauna was shaped by tidal events along the tidelines of marine ecosystems.