Background: To increase psychological well-being and physical activity (PA) behaviors, our pilot study used the social ecological model as the framework to design the 4Active intervention, focusing on multicomponent exercise group lessons at the interpersonal level and self exercise enhanced by activity trackers at the individual level. The purpose of this pilot study was to examine the effectiveness of the two-level 4Active intervention in improving psychological well-being and PA participation in older adults living in retirement communities. Methods: Participants were 27 older adults with a mean age of 85.9 ± 9.3 years. Based on the two-arm, quasi-experimental study design, fourteen older adults (2 men, 12 women) living in one retirement community (RC) were assigned into the intervention group receiving the two-level 4Active intervention, whereas 13 older adults (1 man, 12 women) living in another RC were allocated to the active control group receiving group exercise intervention alone for eight weeks. One week before and after the interventions, the participants were pre-tested and post-tested in psychological well-being (i.e., life satisfaction, subjective happiness, positive affect, and negative affect) and weekly PA minutes (i.e., weekly walking, vigorous, moderate, and total PA minutes). The data were analyzed be means of descriptive statistics, independent sample t-tests, and ANCOVA repeated measures. Results: The results of ANCOVA repeated measures indicated that both groups maintained their slightly high or very high levels of life satisfaction, happiness, and positive affect over times. However, the two-level 4Active intervention group showed significant decreases in negative affect (F = 4.78, p = 0.04, η2 = 0.23) and significance increases in weekly moderate PA (F = 10.355, p = 0.004, η2 = 0.310) compared with the active control group over time. Conclusion: It is concluded that engaging in the two-level 4Active intervention including group-based multicomponent exercises and technology-enhanced self-exercises is more effective in decreasing negative affect and increasing weekly moderate PA METS-min in physically and cognitively frail older adults over time, compared with attending the group exercises alone.