Rare earth elements (REEs) are a group of 15 metals, ranging from lanthanum (La) to lutetium (Lu). Due to their characteristics, the patterns of REEs have been extensively used as tracers in oceanic processes including particle removal, redox changes, and the origin of particles or water masses. Recent studies have shown that submarine groundwater discharge (SGD) may contribute, depending on the characteristics of the area, with comparable or even greater amounts of REEs than those from regional rivers or sedimentary diffusive fluxes. To this end, the processes controlling the behaviour – and therefore the fluxes – of REEs in subterranean estuaries (STE) need to be further explored. An integrated study of continental groundwater discharge was conducted in a large coastal inlet surrounded by a crystalline drainage basin (Ría de Vigo, NW Iberian Peninsula) during July 2023 (dry period) and March 2024 (wet period). Samples were collected at local subterranean estuaries (8), wells (7) and rivers (2), as well as in surface and deep waters of the Ría de Vigo (where a slight gadolinium (Gd) anomaly was detected due to domestic effluents from the WWTPs). Concentrations of total REEs (ΣREEs) were higher in the wells and rivers compared to STE and ría waters. Normalized patterns of REEs were distinctive for each well and river and were in agreement in both sampling campaigns – although higher total concentrations were determined in the wet period – indicating that their distribution is controlled by the lithological setting. Rare earth element patterns at the STE varied at the two sampling dates and did not followed a continuum with respect to the end-members (groundwater and ría waters); instead, the decrease in REEs concentrations at the STE and the appearance of a sharp positive anomaly of the particle-unreactive anthropogenic Gd suggests that STE may act as a sink of dissolved REEs in this area.