Algorithms have been used variously in psychology to address many topics. Nearly all psychological studies’ methodologies are algorithmic, whether implicitly or explicitly. While originally mathematical, algorithms have been used implicitly in domains like applied behavior analysis (ABA)—where procedures are carried out to modify behavior—and explicitly especially in quantitative methodological research. Ontologically, the concept of the algorithm is relevant to the computational model of mind, which is usually distinguished from the phenomenological mind. Algorithms are also relevant for psychological studies of general and domain-specific reasoning, ethics, and potentially morality. Algorithms have been used in the areas of cognitive science (viz., computer science and artificial intelligence), human factors, and psychoinformatics. Algorithms can help psychologists understand phenomena like problem-solving and decision-making, and they can be likened to formal logic. Algorithms can also be of aid in philosophic-psychological argumentation and theory-building. Thus, algorithms have relevance and potential use for theoretical and philosophical psychology.