Abstract
This study evaluates the feasibility and efficacy of “Harness Your Best Self,” a novel internet‐based intervention designed to enhance employee well‐being by leveraging strengths at work, grounded in the Job Demands–Resources theory. The intervention was tested in two phases: a single‐group feasibility study (Study 1) and a waiting‐list randomized controlled trial (RCT, Study 2). Study 1, conducted with working master's students (N = 18), showed high user satisfaction and significant pre–post improvements in work engagement, psychological capital, job satisfaction, and employability (ds = > .44), despite an elevated dropout rate. Study 2, involving early‐career employees, mainly from automotive and IT companies (Intent‐to‐Treat N = 167; Intervention n = 84, Control n = 83), revealed significant post‐intervention improvements, relative to the control group in key outcomes such as work engagement (F[1, 164] = 7.33, p = .007, d = 0.44), strengths use (F[1, 164] = 4.60, p = .033, d = 0.37), and psychological capital (F[1, 164] = 4.28, p = .040, d = 0.28). Secondary outcomes, including job satisfaction (F[1, 164] = 5.24, p = .023, d = 0.30), life satisfaction (F[1, 164] = 5.03, p = .026, d = 0.29), performance (F[1, 164] = 8.44, p = .044, d = 0.41), and employability (F[1, 164] = 4.66, p = .032, d = 0.30) also showed significant gains. Burnout reduction was limited. The effect of the intervention on the main outcomes was serially mediated by the improvements in strengths use and psychological capital. The findings suggest that this online intervention is a promising, scalable tool for promoting well‐being and performance in organizational contexts, with the potential to be refined further for enhanced effectiveness.