The results of a randomized clinical trial (RCT) on the effects of a Tai Chi fall prevention in community-living older people with a high risk of falling in the Netherlands showed no beneficial effects on falls and secondary outcomes (e.g., balance, fear of falling). The aim of this study is to provide insight in process-related factors that may have influenced the effectiveness of the intervention. The intervention consisted of Tai Chi Chuan (TCC) training for 1. h twice a week for 13 weeks. We used self-administered questionnaires and registration forms to collect data from participants and instructors. We analyzed quantitative data by means of descriptive statistics and categorized qualitative data based on the content of the answers given. Of the participants, that started the program 89 (79%) completed the intervention, but a minority of 47% attended 80% of more of the lessons. All participants and instructors were positive about the program and most participants reported benefits from the intervention. Suggestions for improvements mainly relate to adjustments of training aspects. The main process-related factors that may be have influenced the lack of beneficial effects on falls and secondary outcomes are the relatively high withdrawal and the low adherence rates.