Background Physical exercise teletrining can be a good option to maintain intrinsic capacity, especially in confinement situations such as the one experienced during the COVID-19 pandemic. To determine the effect of tele-training tai chi vs. strength exercise on markers of oxidative stress and muscle mass in Mexican older adults during the COVID-19 pandemic. Methods A quasi-experimental exploratory study of a convenience sample of 38 older women who participated in a zoom tele-exercise program, divided into two groups: (i) tai chi group (TCG) n = 19; (ii) strength training group (STG) n = 19. All participants had blood markers of oxidative stress (OxS), inflammation and body composition parameters assessed at baseline and after six months of tele-exercise training. Results Adherence to the tele-training by zoom program was observed in more than 80% of the participants. A statistically significant decrease in the concentration of carbonylated proteins was found in the TCG compared to the STG (TCG, baseline 47.30 ± 5.16, post. 37.09 ± 12.90 vs. STG, baseline, 35.64 ± 13.96, post. 47.68 ± 16.85, p < 0.05), in addition to a decrease in the oxidative stress index (TOS/TAS) in the TCG compared to the STG (TCG, base-line, 9.34 ± 6.88, Post. 5.79 ± 3.95 vs. GST, baseline 5.35 ± 2.39, post 13.24 ± 7.07, p < 0.01). Likewise, a greater increase in the ratio of free fat mass and skeletal muscle mass was observed in the TCG compared to the STG with borderline statistical significance (p = 0.06). Conclusion Our findings suggest that tai chi tele-training by zoom has a significantly greater antioxidant effect than ST linked to an increase in fat-free mass and skeletal muscle mass. Therefore, the use of remote digital platforms, such as zoom, may be an option for healthy aging interventions through the tai chi tele-training to maintain or improve intrinsic capacity.