Introduction. Obsessive-compulsive disorder (OCD) is a disabling condition that can be treated successfully. However, individuals with OCD often fail to seek or delay seeking treatment. In order to overcome this gap and increase the intention to seek for help, a gamified mental health mobile application (app) called esTOCma has been developed with a focus on offering information about OCD and on discussing stigmatizing attitudes toward the disease. The general aim of this study is to analyze the impact of the intervention through esTOCma in a clinical OCD sample. The objective of the study was two-fold. First, to analyze if the intervention changes the following variables in a clinical OCD sample: (1) knowledge about OCD; (2) internalized stigma, guilt, empowerment; and (3) obsessive-compulsive symptoms. Second, to explore satisfaction with the app. Method. Participants were extracted from a total of 330 people who downloaded the app for free and identified themselves as being diagnosed with OCD. From the initial sample, only participants who played till the game was finished and completed a pre- and post-intervention assessment were selected. The final sample comprised 126 (37.4%) participants diagnosed with OCD (mean duration of the disorder 11.56 years; SD=9.73; range 1-45 years). Their mean age was 39.31 years (SD= 39.31; range 18-66), and half of them were women (51.6%). 98.3% had previously asked for help for a mental health problem, and 35.3% belonged to an OCD association. Pre- and post-intervention measures included: (1) mental health literacy about OCD (MHL); (2) the Internalized Stigma of Mental Illness (ISMI); (3) guilt about having OCD (1 item); (4) feeling of empowerment (1 item); (5) Obsessive-Compulsive Inventory-Revised (OCI-R); (6) satisfaction with the app (2 items). Results showed that the intervention produced significant but small effect size changes on the measured variables. After using the app, patients showed higher mental health literacy (t(125)= -3.998, p < .0001; Cohen’s d= .398); lower internalized stigma (t (125)= 3.517, p≤0.001, Cohen’s d=0.312); less guilt associated with OCD (t(125)= 3.592, p< .0001; Cohen’s d=0.265); greater empowerment (t(125)= 3,261, p= .001; Cohen’s d=0.429); and less distress associated with obsessive-compulsive symptoms (t(125)= 3.110, p=.002, Cohen’s d=0.122). Finally, 91.3% (n=115) found the app helpful, and 84.9% (n=107) would recommend it to a friend. Discussion. Results show that the intervention produced significant changes on the variables of interest and that most patients were satisfied with the app. Effect sizes were small, probably due to the fact that patients had already asked for help and had been or were undergoing treatment. Furthermore, a high percentage belonged to OCD associations. Thus, it is expected that participants with these characteristics had prior basic knowledge of OCD and lower stigma than people who have had no prior contact with mental health services.