Architectural design is a complex and dynamic cognitive activity informed by the architect’s intuitions and subjectivity. Self-knowledge becomes significant as architects reflect on their existing knowledge and personal experiences, and translate them into design, shaping their overall design behaviour. Within this view, memory—and particularly autobiographical memory, understood as a dynamic and continually reconstructed cognitive resource—emerges as a key component of self-knowledge. Although design cognition research refers to memory, it has largely treated it as domain-specific knowledge derived from professional practice. Autobiographical memories arising from architects’ spatial experiences, however, have not been examined as a cognitive mechanism, despite their embodied contribution. Extending beyond formal experience, their relevance has mostly been explored within critical theory rather than cognitive perspectives. This study aims to develop a conceptual framework explaining how an architect’s autobiographical memories influence design reasoning and behaviour at a cognitive level. To achieve this, two theoretical frameworks—Adaptive Control of Thought (ACT-R) and the Self-Memory System (SMS)—are integrated within a constructivist epistemology grounded in second-order cybernetics, then adapted to architectural design. An illustrative case study based on Zumthor’s Thinking Architecture is employed, with a limited scope, to manage expectations of empirical generalisation. The findings indicate that autobiographical memories enter design cognition generally through direct retrieval of event-specific knowledge and are proceed in parallel with perceptual attention and spatial imagination. This study contributes design research with a systemic view to analyse dynamic cognitive activity of architects, with future research expected to inform design practice and education through memory-based reasoning.