<p>Introduction: Balance on the Brain is a balance-focused multi-modal community-based exercise intervention aimed at reducing falls and improving health outcomes for people living with mild cognitive impairment (MCI). This study completed an important step when conducting randomised controlled trials (RCTs) by evaluating the barriers and facilitators of the program from the perspective of the intervention participants and the exercise providers delivering the intervention. This study also explored the perspective of the main informal support people (MISP) of intervention participants living with MCI. Methods: This was a qualitative study using face-to-face semi-structured interviews. Interviews were audio-recorded to enable verbatim transcriptions. Braun and Clarke’s 6-step thematic analysis process was used to analyse the data. Results: A total of 26 RCT intervention participants, 4 physiotherapists, and 14 MISPs were interviewed at the end of the 6-month intervention. There was moderate diversity in the overall experiences; for example, what may have been a barrier for some was a facilitator for others. Overall, lack of motivation and other health issues were the most identified barriers across the Balance on the Brain intervention. Key facilitators for the intervention participant were the guidance provided by the physiotherapists delivering the program and the ease of adding the intervention into their daily routine. The MISPs had varying levels of involvement and support throughout the intervention; some completed the intervention exercises with the intervention participant, others were supportive and encouraged participation, and some had no input into the intervention participant’s involvement in the Balance on the Brain intervention. Conclusion: The Balance on the Brain RCT was largely accepted by intervention participants, physiotherapists delivering the intervention, and the MISPs. Exercise interventions that can be tailored to each participant’s needs are likely to be viewed more favourably. Future interventions for this population may be improved by adding opportunities for the MISPs to be more involved. </p>