The present study aims to: • Identify the theoretical foundations and core concepts of Piaget’s theory in explaining cognitive development. • Identify the theoretical foundations and core concepts of Vygotsky’s theory in explaining cognitive development. • Determine the similarities and differences between Piaget’s and Vygotsky’s theories in interpreting cognitive development. • Highlight the educational significance of each theory in the learning process. The study adopted the descriptive-analytical method، which focuses on describing and analyzing psychological phenomena. The research population included all books and articles in the field of cognitive psychology related to Piaget’s and Vygotsky’s theories. The sample was not human; rather، it was limited to selected books and scientific journals relevant to both theories. Through the presentation and analysis of these two theories، the study reached the following findings: Regarding Piaget’s theory: • Piaget explained cognitive development through the self-construction of knowledge، where development occurs as a result of assimilation and accommodation processes. • He emphasized the progression of thinking from sensory-based thinking to abstract thinking. • His theory focused on internal factors and maturation as key drivers of cognitive development. • He proposed four major stages of cognitive development، each characterized by distinctive features that differentiate it from the preceding stage. Regarding Vygotsky’s theory: • Vygotsky interpreted cognitive development as a socio-cognitive process achieved through social interaction. • He indicated that cognitive development involves the transition from lower mental functions to higher mental functions, such as abstract thinking and problem-solving. Both Piaget and Vygotsky agreed that the learner is an active participant in acquiring knowledge and that cognitive development is a gradual process over time. They also rejected the strict behaviorist perspective، emphasizing instead the role of internal mental processes in achieving cognitive growth. However، they differed in their views on the source of cognitive development. Piaget emphasized maturation، whereas Vygotsky stressed the importance of social interaction. They also differed regarding the relationship between development and learning: Piaget believed that cognitive development precedes learning، while Vygotsky argued that effective learning leads to development. Additionally، Piaget viewed language as a product of cognitive development، whereas Vygotsky considered it a fundamental tool that drives cognitive growth. Both theories have significantly contributed to providing conceptual frameworks for understanding cognitive development and offer valuable implications for facilitating learning throughout an individual’s life stages. Keywords: Cognitive development, Piaget's theory, Vygotsky's theory, cognitive psychology.