To maximize the anodic charge storage capacity of Li-ion and Na-ion batteries (LIBs and SIBs, respectively), the conversion-alloying-type Sb2S3 anode has attracted considerable interest because of its merits of a high theoretical capacity of 946 mAh g-1 and a suitable anodic lithiation/delithiation voltage window of 0.1-2 V vs. Li+/Li. Recent advances in nanostructuring of the Sb2S3 anode provide an effective way of mitigating the challenges of structure conversion and volume expansion upon lithiation/sodiation that severely hinder the Sb2S3 cycling stability. In this context, we report uniformly sized colloidal Sb2S3 nanoparticles (NPs) as a model Sb2S3 anode material for LIBs and SIBs to investigate the effect of the primary particle size on the electrochemical performance of the Sb2S3 anode. We found that compared with microcrystalline Sb2S3, smaller ca. 20-25 nm and ca. 180-200 nm Sb2S3 NPs exhibit enhanced cycling stability as anode materials in both rechargeable LIBs and SIBs. Importantly, for the ca. 20-25 nm Sb2S3 NPs, a high initial Li-ion storage capacity of 742 mAh g-1 was achieved at a current density of 2.4 A g-1. At least 55% of this capacity was retained after 1200 cycles, which is among the most stable performance Sb2S3 anodes for LIBs.