Understanding client variables relevant to clinical decision-making is a core feature of psychotherapy. The previous meta-analysis emphasized variables related to stages of psychotherapy, motivational stages of change, alliance, reactance, coping, attachment styles, and emotional stability in psychotherapy outcomes. However, a clinical measure that captures these empirically based clinical variances is missing. The present study describes the development and preliminary analysis of the Clinical Decision-Making Inventory (CDMI) in a sample of individuals engaged in a psychotherapeutic process. One hundred and twenty-three participants (M = 20.28, SD = 5.80) engaged in a psychotherapy process, were assessed in a cross-sectional design. On one hand, the stages of psychotherapy, motivational stages of change, reactance, coping, attachment styles, and emotional stability were negatively correlated with symptomatology, cognitive fusion, interpersonal problems, coping mechanisms, and expressive suppression. On the other hand, correlated positively with metacognition and cognitive reappraisal. Attachment style and emotional stability predicted symptomatology. The CDMI showed promising results; however, more research is required to deepen the psychometric analysis.