**Brief abstract (date: 2022/09/01):** **Introduction** Age-related deficits in dopaminergic neuromodulation play a key role in adult memory decline. Facilitated by technical advancements, recent evidence shows that age-related deficits in noradrenergic neuromodulation also impinge on late-life memory. However, investigations disentangling the relative contributions of the two neuromodulators to the neurobiological basis of human cognitive aging are scarce. **Methods** We collected high-resolution magnetic resonance imaging (MRI) data of the dopaminergic substantia nigra–ventral tegmental area and the noradrenergic locus coeruleus of 320 younger and older adults at two time points (TP1, TP2; ~1.9 years delay). The imaging protocol included three scans sensitive to the substantia nigra–ventral tegmental area and locus coeruleus—a Fast-Spin-Echo [FSE] sequence, and a Magnetization-Transfer sequence, acquired once with a dedicated magnetic saturation pulse [MT+] and once without, resulting in a proton-density image [MT–]. We aggregated the information shared across imaging modalities by estimating multimodal latent factors expressing dopaminergic and noradrenergic integrity. Participants also completed a comprehensive cognitive battery at three time points (TP1, TP2, TP3), including tests of fluid intelligence, episodic and working memory. We used structural equation modeling to evaluate cross-sectional associations of substantia nigra–ventral tegmental area and locus coeruleus integrity with late-life cognition. In a second set of models, we probed longitudinal changes in substantia nigra–ventral tegmental area and locus coeruleus integrity (TP1–TP2) and used them to predict participants’ future cognitive performance (at TP3). **Results** Cross-sectionally, we found differential associations of dopaminergic and noradrenergic nuclei with late-life cognition. While locus coeruleus integrity was related to better episodic memory across several memory tasks, substantia nigra–ventral tegmental area integrity was related to working memory performance. Moreover, consistent with a largely shared biosynthesis of the neuromodulators, dopaminergic and noradrenergic nuclei were positively related. Longitudinally, we found that older age was associated with more-negative change in substantia nigra–ventral tegmental area and locus coeruleus integrity (TP1–TP2). Importantly, changes in locus coeruleus integrity reliably predicted future episodic memory performance (at TP3). **Discussion** These findings support the utility of in-vivo indices for catecholaminergic integrity and point to differential roles of dopaminergic and noradrenergic neuromodulation in late-life cognitive decline.