Tai Chi is an effective exercise option for individuals with coronary heart disease or its associated risk factors. An accurate and systematic assessment of a Mandarin-speaking adults’ self-efficacy in maintaining Tai Chi exercise is lacking. Mandarin Chinese has the most speakers worldwide. This study aimed to translate the Tai Chi Exercise Self-Efficacy scale and examine its psychometric properties. The 14-item Tai Chi Exercise Self-Efficacy scale was translated from English into Mandarin Chinese using a forward-translation, back-translation, committee approach, and pre-test procedure. Participants with coronary heart disease or risk factors (n = 140) enrolled in a cross-sectional study for scale validation. Confirmatory factor analysis indicated a good fit of the two-factor structure (Tai Chi exercise self-efficacy barriers and performance) to this sample. The translated scale demonstrated high internal consistency, with a Cronbach’s α value of 0.97, and good test-retest reliability, with an intra-class correlation coefficient of 0.86 (p < 0.01). Participants with prior Tai Chi experience reported significantly higher scores than those without (p < 0.001), supporting known-group validity. A significant correlation was observed between the translated scale and total exercise per week (r = 0.37, p < 0.01), providing evidence of concurrent validity. The Mandarin Chinese version of the Tai Chi Exercise Self-Efficacy scale is a valid and reliable scale for Chinese adults with coronary heart disease or risk factors.