<p>A key scientific approach to addressing the environmental radiation risks from Fukushima nuclear contaminated water (FNCW) discharge into the ocean is understanding and predicting the marine dispersion of radionuclides. The dispersion of radiocesium (Cs_F: ¹³⁴Cs, ¹³⁷Cs) from the Fukushima nuclear accident in the North Pacific and its marginal seas post-2011 was systematically summarized, focusing on pathways, vertical distribution changes, and transit times. Our research examined Cs_F dispersion through the Kuroshio Extension and denser central mode water (D-CMW) to the eastern North Pacific, as well as through subtropical mode water (STMW), lighter central mode water (L-CMW), and D-CMW to the subtropical western North Pacific, China Seas, and Sea of Japan. We considered broader implications of Cs_F dispersion in light of ongoing FNCW discharge. Given this prolonged liquid discharge and Kuroshio Extension’s barrier effect, it is crucial to emphasize the role of CMW besides STMW in transporting FNCW to the subtropical western North Pacific and its marginal seas. Future research should focus on the key mechanism and longitude range of CMW crossing the Kuroshio Extension. Since short-lived ¹³⁴Cs decays rapidly during the storage and dispersion of FNCW, long-lived ¹³⁵Cs and ¹³⁵Cs/¹³⁷Cs ratios can serve as valuable tracers for detecting and quantifying FNCW. Therefore, there is an urgent need for high-precision analysis of these key radionuclides and their characteristic ratios. To promptly detect, assess, and respond to FNCW intrusion, continuous monitoring and identification of nuclear pollution sources in key ocean currents and straits are critical. Furthermore, interdisciplinary research integrating monitoring with marginal sea circulation dynamics and high-resolution numerical simulations should be a priority.</p>