There is substantial evidence to support the idea that physical activity leads to health benefits for older adults. These benefits include a decreased rate of falls and fall-related injuries, osteoporosis, and dementia. Despite the numerous benefits of physical activity, many older adults do not meet the recommended physical activity guidelines. Motivational interviewing (MI) is a client-centred counselling style for strengthening motivation for change. MI has shown to be promising in the general adult population for improving physical activity levels. However, evidence is lacking to support MI's effectiveness in physical activity among older adults. This thesis has four objectives: 1) to synthesize evidence on the effect of MI on physical activity among older adults 2) to determine the feasibility of using virtual MI to improve physical activity among community-dwelling older adults 3) to explore the experiences of older adults and counsellors involved in virtual MI and 4) to examine the influence of counsellors’ behaviours and skills on participants’ change and sustain talk during MI sessions. For objective 1, a systematic review and meta-analysis was conducted. Objective 2 was achieved using a feasibility study with a single-group pre- and post-design. A qualitative descriptive design guided the data collection and analysis for objective 3. Lastly, objective 4 utilized a sequential observational method to examine the transition between the counsellors’ behaviours and participants’ utterances. The meta-analysis of three trials showed that the effect of MI on physical activity among older adults was not different between treatment and control groups. The findings from the feasibility study show that virtual MI should be a feasible and acceptable approach for improving physical activity among older adults. From the experiences of older adults and counsellors using virtual MI, we identified the interconnections between technology, relationships between older adults and counsellors, and MI skills and principles. Virtual MI was described as convenient and flexible. In the sequential analysis, all counsellors’ behaviours elicited participants’ change talk. MI-consistent behaviours elicited both change and sustain talk. This thesis adds to the literature by using different approaches and methods to examine the novel use of virtual MI for physical activity among older adults.