Alexithymia is a personality construct characterized by the inability to identify and describe emotions. The core characteristics of alexithymia are a marked dysfunction in emotional awareness, social attachment, and interpersonal relating. Furthermore, alexithymics have difficulty in distinguishing and appreciating the emotions of others, which is thought to lead to unempathic and ineffective emotional responding. Alexithymia is prevalent in approximately 10% of the general population and is known to be comorbid with a number of psychiatric conditions. Research shows that it is common among individuals with substance use disorders, suggesting that it is a trait that may contribute to substance dependence. This paper will review alexithymia as it relates to substance use and substance use disorders, considering its potential role in the maintenance and treatment of these disorders.