Research suggests that tests of memory fidelity, feature binding and spatial navigation are promising for early detection of subtle behavioural changes related to Alzheimer’s disease (AD). In the absence of longitudinal data, one way of testing the early detection potential of cognitive tasks is through the comparison of individuals at different genetic risk for AD. Most studies have done so using samples aged 70 years or older. Here, we tested whether memory fidelity of long-term object-location binding may be a sensitive marker even among cognitively healthy individuals in their mid-60s by comparing participants at low and higher risk based on presence of the ε4-allele of the apolipoprotein gene (n=26 ε3ε3 and n=20 ε3ε4 carriers). We used a continuous report paradigm in a visual memory task that required participants to recreate the spatial position of objects in a scene. We employed mixture modelling to estimate the two distinct memory processes that underpin the trial-by-trial variation in localisation errors: retrieval success which indexes the proportion of trials where participants recalled any information about an object’s position and the precision with which participants retrieved this information. Prior work has shown that these memory paradigms that separate retrieval success from precision are capable of detecting subtle differences in mnemonic fidelity even when retrieval success could not. Nonetheless, a Bayesian analysis found good evidence that ε3ε4 carriers did not remember fewer object locations (F(1, 42)=.450, p=.506, BF01=3.02), nor was their precision for the spatial position of objects reduced compared to ε3ε3 carriers (F(1, 42)=.12, p=.726, BF01=3.19). Importantly, ε3ε4- carriers from the same sample have previously been reported to exhibit wayfinding deficits in a spatial navigation task (Coughlan et al. 2019, PNAS, 116(19)). The sensitivity of memory fidelity tasks may therefore not extend to individuals with one ε4-allele in their early to mid- 60s. These results provide further support to prior proposals that spatial navigation may be a sensitive marker for the earliest AD-dependent cognitive changes, even before episodic memory. More research in preclinical AD is needed to confirm this hypothesis by direct comparison of memory fidelity and spatial navigation tasks.