Rare earth elements and yttrium (REY) are often used as proxies for (paleo)environmental conditions and for the reconstruction of element sources and transport pathways. Many geological systems are well described with respect to the behavior of REY but deep-sea sediments with their manifold processes impacting the sediment during early diagenesis leave some questions about the origin and development of the shale-normalized REY (REY SN ) patterns unanswered. Here we report REY data for sediment solid phase and pore water from the upper 10 m of deep-sea sediments from the Clarion Clipperton Zone (CCZ) in the central equatorial Pacific. The solid-phase REY profiles show highest concentrations at depth below 5–8 m. The REY SN patterns show an enrichment in middle REY (MREY) (La SN /Gd SN between 0.35 and 0.60; Gd SN /Yb SN between 1.19 and 1.47) and either no or negative Ce SN and Y SN anomalies (i.e. chondritic to sub-chondritic Y/Ho ratios between 24.7 and 28.7). Based on correlation analyses of bulk sediment element concentrations and sequential extractions, we suggest that a Ca phosphate phase controls the distribution and the patterns of REY in these silty clay pelagic sediments rich in siliceous ooze. The MREY enrichment develops at the sediment-water interface and intensifies systematically with depth. The negative Ce SN anomaly intensifies with depth possibly because Ce is mostly bound to Mn- and Fe-(oxyhydr)oxides. Therefore, Ce concentrations remain relatively constant throughout the sediment core, while its trivalent REY neighbors are mostly hosted by the Ca phosphate phase that continuously incorporates REY from ambient pore waters. The non-redox-sensitive trivalent REY concentrations increase with depth, producing or enhancing a negative Ce SN anomaly through coupled substitution of REY 3+ and Na + for Ca 2+ . The solid-phase REY SN pattern is therefore determined by the pore-water REY SN pattern and not suitable for paleoceanographic interpretation. The similarity of the pore-water and solid-phase REY SN patterns suggests, however, that only minor fractionation occurs during REY incorporation into the Ca phosphate crystal structure.