18.6-year period variability has been detected in various aspects of the climate, especially in and around the Pacific Ocean. Although it is believed to be caused by 18.6-year period tidal cycle, no study has directly shown how the tidal cycle regulates such variability. Using a state-of-the-art climate model, we show that the 18.6-year cycle in strong tidal mixing localized around the Kuril Islands induces 18.6-year periodicity in El Nino-Southern Oscillation-like Pacific climate variability. Influence of the tidal mixing propagates along the Pacific western rim as coastally trapped waves. Temperature anomaly is generated in the subsurface western equatorial Pacific, which propagates along the equatorial thermocline and eventually excites 18.6-year periodicity in the equatorial sea surface temperature.