AbstractMemory‐related functional magnetic resonance imaging (fMRI) activations show age‐related differences across multiple brain regions that can be captured in summary statistics like single‐value scores. Recently, we described two single‐value scores reflecting deviations from prototypical whole‐brain fMRI activity of young adults during novelty processing and successful encoding. Here, we investigate the brain‐behavior associations of these scores with age‐related neurocognitive changes in 153 healthy middle‐aged and older adults. All scores were associated with episodic recall performance. The memory network scores, but not the novelty network scores, additionally correlated with medial temporal gray matter and other neuropsychological measures including flexibility. Our results thus suggest that novelty‐network‐based fMRI scores show high brain‐behavior associations with episodic memory and that encoding‐network‐based fMRI scores additionally capture individual differences in other aging‐related functions. More generally, our results suggest that single‐value scores of memory‐related fMRI provide a comprehensive measure of individual differences in network dysfunction that may contribute to age‐related cognitive decline.