The lacrimal gland (LG) secretes aqueous tears. Previous studies have provided insights into the cell lineage relationships during tissue morphogenesis. However, little is known about the cell types composing the adult LG and their progenitors. Using scRNAseq, we established the first comprehensive cell atlas of the adult mouse LG to investigate the cell hierarchy, its secretory repertoire, and the sex differences. Our analysis uncovered the complexity of the stromal landscape. Epithelium subclustering revealed myoepithelial cells, acinar subsets, and two novel acinar subpopulations:TfrchiandCar6hicells. The ductal compartment containedWfdc2+multilayered ducts and anLtf+cluster formed by luminal and intercalated duct cells.Kit+progenitors were identified as:Krt14+basal ductal cells,Aldh1a1+cells ofLtf+ducts, andSox10+ cells of theCar6hiacinar andLtf+epithelial clusters. Lineage tracing experiments revealed that theSox10+ adult populations contribute to the myoepithelial, acinar, and ductal lineages. Using scRNAseq data, we found that the postnatally developing LG epithelium harbored key features of putative adult progenitors. Finally, we showed that acinar cells produce most of the sex-biased lipocalins and secretoglobins detected in mouse tears. Our study provides a wealth of new data on LG maintenance and identifies the cellular origin of sex-biased tear components.