The high-temperature requirement A1 (HTRA1), a serine protease, has been demonstrated to play a pivotal role in the extracellular matrix (ECM) and has been reported to be associated with the pathogenesis of age-related macular degeneration (AMD). To delineate its role in the retina, the phenotype of homozygous Htra1-KO (Htra1-/-) mice was characterized to examine the effect of Htra1 loss on the retina and retinal pigment epithelium (RPE) with age. The ablation of Htra1 led to a significant reduction in rod and cone photoreceptor function, primary cone abnormalities followed by rods, and atrophy in the RPE compared with WT mice. Ultrastructural analysis of Htra1-/- mice revealed RPE and Bruch's membrane (BM) abnormalities, including the presence of sub-RPE deposits at 5 months (m) that progressed with age accompanied by increased severity of pathology. Htra1-/- mice also displayed alterations in key markers for inflammation, autophagy, and lipid metabolism in the retina. These results highlight the crucial role of HTRA1 in the retina and RPE. Furthermore, this study allows for the Htra1-/- mouse model to be utilized for deciphering mechanisms that lead to sub-RPE deposit phenotypes including AMD.