Cognitive-behavioral therapy (CBT) encompasses various psychotherapeutic approaches that are rooted in the fundamental principle that a person’s thinking is the prime determinant of emotional and behavioral responses to life situations. The historical influences of CBT can be found in the behavioral approaches: John Watson’s classical conditioning and B. F. Skinner’s operant conditioning, with their focus on antecedents and reinforcers of behavior and an empirical approach to evaluating behavior; Albert Bandura’s social-learning theory and social-cognitive theory, with a focus on observational or vicarious learning; and George Kelly’s personal-constructs theory. Other influences that shaped the philosophical foundations of CBT include Greek and Roman Stoicism and the Eastern philosophies of Buddhism and Taoism, with their emphasis on reason, logic, acceptance, and mindfulness. CBT as an organized system of psychotherapy began to emerge in the 1950s and 1960s with the works of Albert Ellis’s rational-emotive behavior therapy (REBT) and Aaron Beck’s cognitive therapy (CT). Both these models stress that cognitions, in the form of judgments, meanings, attributions, and assumptions tied to life events, are the primary factors that influence how individuals respond to environmental cues. The CBT emphasis on internal, private, conscious thought represented a departure from psychoanalytic theory, which emphasizes unconscious motivation of behavior, as well as from behaviorism, with its focus on external observable and measurable behaviors. The various cognitive-behavioral approaches share a number of similarities that include a focus on conscious thinking; the importance laid on information processing and the role that cognitions play in how we process information from our environment and respond to situations; and the assumption that, by changing irrational or maladaptive thoughts in a more rational, logical, realistic, and balanced perspective, people are capable of increasing healthy functioning. CBT is a present-oriented, relatively brief, structured, problem-focused, empirically driven form of psychotherapy. In CBT both the clinician and the client take an active approach in addressing the client’s problem. In a nutshell, the therapeutic work revolves around identifying maladaptive thinking, assessing the validity and functionality of such thoughts by evaluating available evidence for or against the thoughts, and formulating a more rational, logical, realistic, and balanced approach to interpreting one’s reality. In the late 20th and early 21st centuries, various models of CBT have been applied to a wide range of mental health problems, substance abuse issues, and other disorders. More importantly, CBT continues to generate voluminous research studies, articles, and books, discussing its application across various disorders and with diverse populations, making it one of the most empirically based systems of psychotherapy. Although an all-inclusive review of CBT-related works is not possible here, we have selected works that will either help the readers get a better understanding and insight into various aspects of CBT or pique their curiosity to seek additional information on their own. For this purpose, we have included newer material along with older works that we consider to be important in the context of the history and evolution of CBT and that have become essential readings for those interested in CBT.