Primary acquired nasolacrimal duct obstruction (PANDO) is a common cause of adult epiphora, yet the biochemical environment within the nasolacrimal duct (NLD) remains poorly understood. This study aimed to characterize the proteomic composition of NLD lavage fluid and to identify subtype specific molecular features associated with membra-nous and mucinous obstruction. Paired tear and NLD fluid samples were collected from patients undergoing dacryoendoscopic recanalization, and proteomic profiling was per-formed using LC–MS/MS. A total of 1,345 proteins were identified in NLD lavage fluid and 767 in tear fluid, with only partial overlap, revealing a distinct NLD-specific proteome. Although the membranous and mucinous subtypes shared broadly similar protein com-positions, differentially expressed proteins highlighted divergent biological pathways. The membranous subtype showed enrichment of keratinization related processes involv-ing KRT1, KRT9, and KLK13, suggesting epithelial remodeling and cornification. In con-trast, the mucinous subtype exhibited upregulation of proteins linked to lipid, carboxylic acid, and sulfur compound metabolism, including ALOX15B, LCAT, and GSTM4, indi-cating metabolic conditions that promote mucin–lipid interactions, glycan sulfation, and redox dependent mucin cross linking. These findings demonstrate that PANDO com-prises biologically distinct obstruction subtypes and provide molecular insights that may support the development of subtype specific diagnostic or therapeutic approaches.