A recent study (Pang & Ruch, 2018) suggested that mindfulness and character strengths mutually enhance one another, creating a dynamic of an upward spiral. Based on these interconnections, the present study examined the effectiveness of a training combining the two practices regarding well-being and work-related outcomes. A total of 63 participants from various job branches were randomly assigned to three conditions: (1) Mindfulness-Based Strengths Practice (MBSP); (2) Mindfulness-Based Stress Reduction (MBSR); and (3) Wait-list Control. Participants’ well-being, perceived stress, job satisfaction, and task performance (supervisor rating) were assessed before and after the intervention, and 1-, 3-, and 6 months afterwards. A set of linear mixed-effects models was applied, modelling changes in participants’ outcome variables over time. Results showed the MBSR was effective for increasing well-being, reducing perceived stress, and increasing job satisfaction, whereas the MBSP was effective for increasing job satisfaction and task performance. These findings provided some indirect evidence on the upward spiral process of mindfulness and character strengths. With the help of mindfulness, participants are more aware of their own strengths and more attentive to apply their strengths. This creates a better fit between their personal strengths and their organizations, which further contributes to their improvement in performance.