According to the United Nations World Population Prospects 2017, one of the fastest growing populations globally are older adults, aged 60 and above (United Nations Department of Economic and Social Affairs- Population Division, 2017). Indeed, it is predicted that the number of older adults will increase from an estimation of 962 million in 2017 to 2.1 billion in 2050. Given this predicted trend in population ageing, there is a critical need for investigations on interventions that may promote healthy ageing. In this context, a growing body of studies have suggested that mindfulness-based interventions (MBIs) could be effective in improving well-being (Greiger et al., 2016) and reducing neurocognitive declines in ageing (Gard, Hölzel, & Lazar, 2014; Malinowski, Moore, Mead & Gruber, 2014) and age-related diseases, such as AD (Larouche, Hudon, & Goulet, 2014; Wells et al., 2013). However, empirical investigations of MBIs with older adults are limited, and few studies have explored the psychological mechanisms by which MBIs may impact markers of ageing and AD. As such, this PhD study aimed to provide insights into the psychological and neurocognitive effects of an MBI with older adults and possible underlying psychological mechanisms. The first chapter of this thesis described the cognitive and brain changes that occur across an ageing spectrum. In addition, theories of ageing and interventions that may promote successful ageing were discussed. MBIs were considered as potential interventions in aging, and research on mindfulness with older adults was reviewed. Chapters 2 and 3 detailed the methodology used in this PhD study, including Electroencephalography (EEG)/Event-related potentials (ERPs) and Proton Magnetic Resonance Spectroscopy (1H-MRS). Chapter 4 provided a critical, theoretical review on the potential of MBIs in preventing or delaying the offset of AD. In particular, the review highlighted the roles of stress in AD pathology, and considered the psychological and psychophysiological mechanisms that MBIs may impact the stress process. Chapters 5 and 6 presented a feasibility-pilot investigation utilising 1H-MRS and an ERP study using a pseudo-randomised wait-list controlled design, that examined the effects of an eight-week standardised Mindfulness-Based Stress Reduction (MBSR) course with typically ageing older adults. Findings from these investigations indicated limited effects of an MBSR course on physiological measures associated with ageing and AD, including neurometabolites (N-Acetyl Aspartate, myo-Inositol, Creatine, gamma-Aminobutryric acid, and Glutamate) and Event-Related Potential Components (N400 and P600). However, improvements in self-report levels of stress, neuroticism, depression, and well-being were documented for the training group following the MBSR course. Chapter 7 considered the findings and implications of this PhD study in relation to the limitations. It also proposes recommendations for future research in this area.