Kamphaugite-(Y) occurs as white to cream-coloured spherical to semi-spherical aggregates of radial crystals in the La Cabrera granitic pluton (Spanish Central System). It mainly occurs on the free surfaces of alkali feldspar, quartz, calcite, kainosite-(Y) and laumontite, and inside miarolitic cavities. La Cabrera kamphaugite-(Y) has an average composition of Ca0.94Y0.89REE0.21(CO3)2 [F0.05(OH)0.95]·1.19H2O. Negative δ13CV-PDB values (−14 to −15‰) indicate a meteoric carbon source. Textural relations between kamphaugite-(Y) and coexisting minerals, its relatively high δ18OV-SMOW values (+25 to +26‰), and the occurrence of laumontite inclusions in kamphaugite-(Y), point to a genesis at <50°C during very low-temperature post-magmatic hydrothermal activity.