The structure of silver centers formed at different femtosecond laser direct writing speeds in zinc-phosphate glass co-doped with Ag⁺ and Nd³⁺ ions was determined using X-ray absorption spectroscopy, optical absorption spectroscopy and transmission electron microscopy. It was established that at laser writing speeds from 1 to 10 μm/s, the formation of sub-nanometer nanoclusters (NCs) and predominantly small (≤2 nm) silver nanoparticles (NPs) occured within the laser-written tracks, with no distinct boundary observed between the sizes of NCs and NPs. A negligible number of silver NPs larger than 3-5 nm were also presented. The formation of silver NPs in the tracks was confirmed by a well-defined localized surface plasmon resonance (LSPR) band in the optical absorption spectra of these glass regions for writing speeds ≤10 μm/s. The dependence of the LSPR characteristics on the laser writing speed revealed that silver NPs formed at speeds ≤5 μm/s possess the most pronounced resonance, centered at a wavelength of ~450 nm. Variations in the writing speed significantly affected the LSPR intensity but only slightly shifted its spectral position, indicating the absence of both NPs aggregates and large NPs. The fraction of silver ions bounded to oxygen and the fraction of Ag atoms incorporated into silver NCs/NPs within the laser tracks were estimated. As a result of laser processing, neodymium ions remained in the Nd³⁺ state and did not form significant aggregates within the tracks. The obtained results advance the development of laser direct writing for the spatial design of plasmonic nanostructures with the determined size and agglomeration degree in glasses co-doped with plasmonic and rare-earth metal ions. Keywords: Zinc-phosphate glass, direct recording method by femtosecond laser, silver nanoclusters/nanoparticles, localized surface plasmon resonance, local electric field.