Disorganization has been considered as a clinical domain close to the core of psychosis. However, it has received poor attention, especially at the illness onset. Moreover, most of the studies examining disorganized symptoms have been conducted in patients with chronic psychosis and research in the early stages of illness is still relatively scarce. Thus, the aims of this study were (a) to longitudinally monitor the stability of disorganization in patients with first episode psychosis (FEP) across a 1-year follow-up period, and (b) to investigate any relevant association of disorganized symptoms with functioning, psychopathology and the specific treatment components of an 'early intervention in psychosis' (EIP) program along the 1year of follow-up. At baseline, 312 FEP participants (aged 12-35 years) completed the positive and negative syndrome scale (PANSS) and the global assessment of functioning (GAF). Spearman's correlations and multiple linear regression analysis were used. At baseline, disorganization showed significant associations with all PANSS subscores, and a relevant negative correlation with GAF score. Across the follow-up, FEP individuals showed a significant improvement in disorganization severity. This decrease was specifically related to both baseline antipsychotic dosage and the number of individual cognitive-behavioural therapy sessions offered across the 1-year follow-up period. Disorganization is clinically relevant in FEP patients, already ate the enrollment in an EIP program. However, it tends to improve over time together with the delivery of specialized, person-tailored FEP interventions within a specific EIP protocol.