We investigated whether older adults without subjective memory complaints, but who present with cognitive decline in the laboratory, demonstrate atrophy in medial temporal lobe (MTL) subregions associated with Alzheimer's disease. Forty community-dwelling older adults were categorized based on Montreal Cognitive Assessment (MoCA) performance. Total grey/white matter, cerebrospinal fluid, and white matter hyperintensity load were quantified from whole-brain T1-weighted and FLAIR magnetic resonance imaging scans, while hippocampal subfields and MTL cortical subregion volumes (CA1, dentate gyrus/CA2/3, subiculum, anterolateral and posteromedial entorhinal, perirhinal, and parahippocampal cortices) were quantified using high-resolution T2-weighted scans. Cognitive status was evaluated using standard neuropsychological assessments. No significant differences were found in the whole-brain measures. However, MTL volumetry revealed that anterolateral entorhinal cortex (alERC) volume -- the same region in which Alzheimer's pathology originates -- was strongly associated with MoCA performance. This is the first study to demonstrate that alERC volume is related to cognitive decline in preclinical, community-dwelling older adults.