To explore the distribution characteristics and influencing factors of rare earth elements (REEs) in coastal sediment and to determine the source of the sediment, the REE contents of coastal sediments in tropical China were systematically determined and analysed. REEs (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y) were analysed by inductively coupled plasma mass spectrometry (ICP-MS). The sediment particulate diameter was determined with a particle size analyser. The results showed that the average value of ΣREE is 260.123 μg.g⁻¹. Due to the effect of the sediment particulate diameter and seawater leaching, the lowest ΣREE in vertical distribution was observed in layer A (0–5 cm), and the highest ΣREE was observed in layer B (10–15 cm). The chondrite-normalised patterns of REEs in the study area were characterised by the enrichment of light rare earth elements (LREEs), the relative depletion of heavy rare earth elements (HREEs), and a negative europium (Eu) anomaly; these patterns are similar to the reported REE characteristics of the surrounding sediments and terrestrial soils. The largest REE contribution to the sediment in the study area was from granite. The distribution and enrichment of ΣREE in mudflat, forest edge and forest interior sediments were not affected by the particulate diameter. The REEs are mainly derived from land sources and are partially affected by marine deposition and anthropogenic disturbances.