Crust–mantle interaction and arc magmatism in subduction zones record the global recycling of elements from Earth's surface to its interior. Nb-enriched basalts are specific to arc settings and are generated through the partial melting of heterogeneous mantle sources or mantle wedge metasomatised by subducted slab-derived melts. However, it is unclear what role subducted sediments play in the formation of Nb-enriched basalts. We present the first report of Cambrian Nb-enriched basalts at A'qiang and Pulu in the Western Kunlun Orogen (NW China), which might have formed above a subducted ridge-related slab window. The A'qiang basalts (Nb = 6.7–7.7 ppm) exhibit E-MORB-like geochemical characteristics, with positive Nb and Ta anomalies, high Mo/Ce ratios (∼0.02), and positive εNd(t) (4.9–5.0) and low δ98/95Mo (−0.74‰ to −0.21‰) values. These basalts were generated through the partial melting of sub-slab asthenosphere modified by minor altered ocean crust and/or marly sediments. In contrast, the Pulu basalts (Nb = https://doi.org/10.9–13.7 ppm) are characterised by enrichment in light rare earth elements (LREEs), high Th/Ce (>0.1) and low Mo/Ce (∼0.001) ratios, negative εNd(t) (−1.5 to −1.1) and mantle-like zircon δ18O values (4.25‰–5.69‰), and high δ98/95Mo values (−0.03‰ to +1.17‰). The Pulu Nb-enriched basalts were derived from the partial melting of sub-slab asthenosphere modified by moderate siliciclastic sediments. Therefore, we propose that subducted sediments play a vital role in the transport of high field strength elements back into the mantle and their recycling into the crust, for example through the formation of Nb-enriched basalts.