<p>To manage the water supply and prevent saltwater intrusion, estuary dams have been constructed, which obstruct water flow and affect biogeochemical processes in estuarine environments. To investigate the influences of the estuary dam on the behavior of dissolved rare earth elements (REEs), we collected seasonal water samples from the Nakdong River Estuary, Busan, Korea, where an estuary dam is present. The distribution of the dissolved REEs showed contrasting trends depending on the element and season. The post-Archean Australian shale-normalized patterns along the Nakdong River Estuary clearly showed three different trends: (1) high Yb_SN/Nd_SN ratios (30 ± 1) with low Ce anomalies (0.4 ± &lt; 0.1) upstream of the dam in winter, (2) low Yb_SN/Nd_SN ratios (4.0 ± 0.4) with high Ce anomalies (0.9 ± 0.1) upstream of the dam in summer, and (3) low Yb_SN/Nd_SN ratios (4.8 ± 1.3) with low Ce anomalies (0.4 ± &lt; 0.1) downstream of the dam in both seasons. However, at all sampling sites, anthropogenic Gd (Gd_anth) concentrations showed negative correlations with salinity in both seasons (<i>r</i> = − 0.997; <i>p</i> &lt; 0.001 in winter and <i>r</i> = − 0.986; p &lt; 0.001 in summer), indicating that the presence of the estuary dam does not seem to affect Gd_anth distribution. In winter, although approximately 10 times higher Gd_anth concentration (43.4 ± 53.4 pM) were calculated compared with that in summer (4.5 ± 4.8 pM), a relatively lower Gd_anth flux (18.4 ± 1.11 M month⁻¹), compared with that in summer (26.2 ± 2.86 M month⁻¹), was estimated because of low discharge rates. Overall, our results indicate that dissolved REEs, including Gd_anth, can exhibit contrasting seasonal behaviors in the estuary dam system.</p>