Bipolar disorder (BD) and autism spectrum disorder (ASD) are both highly heritable, with BD showing a heritability of 60–90% and ASD ranging from 64% to 91%. BD typically develops from childhood anxiety and sleep disturbances into depressive symptoms during adolescence and progresses to manic or hypomanic episodes in early adulthood. Early signs of BD are frequently misdiagnosed as unipolar depression or anxiety disorders. Those young individuals with a familial predisposition who exhibit mood and anxiety and are at an increased risk of developing full-blown BD demonstrate a latent form of BD. ASD and BD share overlapping symptoms, including irritability, impulsivity, social deficits, executive function impairments, sleep disturbances, and sensory sensitivities. These similarities, along with co-occurring conditions such as attention deficit hyperactivity disorder, anxiety disorders, and substance use disorders, make accurate diagnosis challenging. For clinicians, recognizing these overlapping symptoms is essential, particularly in cases of latent or subtle BD, which adds a layer of complexity. This chapter aims to explore the interplay between BD and ASD to improve understanding and diagnostic approaches for ASD within the context of latent BD, focusing mainly on adolescents and adults who need minimal support.