Background. Bipolar disorder (BD) is a chronic affective mental disorder characterized by cycling affective episodes. Its prognosis depends on several factors such as age, sex or comorbidities. In this review, we will focus on the so-called ”duration of untreated bipolar disorder” (DUB), defined as the period between the onset of the patient’s symptoms and the start of an appropriate treatment, since it may have an influence on the recovery of BD patients. Objectives. The main objective is to assess the association between the DUB and the clinical outcomes of patients with BD and to highlight the importance of reducing the DUB to improve the prognosis of this disease. Methods. The search strategy is based on using Mesh descriptors in different databases: PubMed, Scopus, and Cochrane Library. Then, 15 articles were finally selected. The results obtained have been reflected for subsequent systematic evaluation. Results. A prolonged DUB is associated with the presence of BD subtype II, a longer duration of the illness, an early age of onset, a first episode of depressive polarity, a higher number of affective episodes of depressive type, and a higher number of suicide attempts. Limitations: The concept of DUB lacks consensus leading to varied terminology and limited research. Unlike psychotic disorders, there’s no standardized tool to measure DUB. Conclusions. DUB appears to be a modifiable factor linked to poorer outcomes in BD patients. Minimizing DUB is crucial for enhancing the long-term management of BD. Tailored early treatment strategies might be implemented to address this.