Perceived improvement has been proposed as an important patient-reported outcome measure in mental health services evaluation. One advantage of this measure is that it can indicate whether other outcome measures, as pre-post differences in symptoms, correspond to a noticeable impact in patients' lives, as assessed by themselves. This study investigated the association between observer and self-reported symptomatic changes and perceived improvement by patients treated in two Brazilian outpatient mental health services. Significant and positive correlations were found between perceived improvement scores and both pre-post differences, obtained in observer-reported and patient-reported symptom scores. Nevertheless, scores of perceived improvement showed to be more correlated to patient-reported than to the observer-rated symptomatic change score. In addition, a greater correlation was found between perceived improvement scores and post-treatment symptom scores, compared to pre-treatment. These results suggest that an improvement in symptom severity, measured by pre-post differences scores, corresponds to the patient perception that he is actually better than before. However, the correlations found were moderate, suggesting that other factors may also be related to perceived improvement and must be investigated in further studies.