Introduction: Alliance is an essential component of all psychotherapies and a consistent predictor of its outcomes. The Working Alliance Inventory (WAI) is a widely used and psychometrically sound measure of alliance. It assesses three key aspects of the construct: a) agreement on the tasks of therapy; b) agreement on the therapeutic goals; and c) development of an affective bond. Objective: To preliminarily analyze the psychometric properties of the Brazilian version of both the original, 36-item WAI, and of the short form revised, 16-item version (WAI-SR). Methods: The sample comprised 201 psychodynamic psychotherapy patients. Alliance assessments were made after the 4th treatment session. Results: The inventory adapted to Brazilian Portuguese, in both the original and short forms, appears to be reliable and valid to measure alliance and its dimensions by clients in psychotherapy. Further studies are needed to replicate and expand the findings.