Objective <p>Patients at risk of dementia, such as those with subjective cognitive decline (SCD) and mild cognitive impairment (MCI), present with specific clinical symptoms, as well as functional and structural changes within the brain. Dispositional mindfulness (DM) has been linked to better cognition and is associated with activation and grey matter volume changes in specific brain regions in healthy adults. This study aimed to investigate how DM changes along the trajectory of cognitive decline in patients at risk for AD and to identify the brain structures that may be responsible for these changes in DM.</p> Method <p>In total, 79 older adults (SCD = 48, MCI = 31) underwent cognitive testing and brain MRI volumetry, resting-state functional MRI derived connectivity, and diffusion-weighted imaging. DM was assessed with the Breath Counting Task (BCT).</p> Results <p>Participants with MCI showed worse mean counting accuracy in the BCT compared to those with SCD (adjusted <i>p</i> &lt; 0.001). Higher functional connectivity of the ventromedial prefrontal cortex predicted greater counting accuracy in MCI, but not in SCD. The difference between MCI and SCD in regression slope was also statistically significant for ventromedial prefrontal cortex functional connectivity (adjusted <i>p</i> = 0.002). No other statistically significant associations were found between DM, MRI indices, and neuropsychological variables in either group.</p> Conclusion <p>MCI and SCD were associated with distinctly different levels of DM, possibly due to more severe cognitive decline in MCI. Functional changes in ventromedial prefrontal cortex in MCI could play a key role in the worsening of DM in this population.</p> Preregistration <p>This study is not preregistered.</p>