Abductive reasoning is widely recognized as a fundamental core of design thinking; understanding it is therefore essential to the design domain, particularly in relation to how it operates within architectural design practice. Such understanding requires a comprehensive examination of abductive reasoning in terms of its conceptual dimensions and characteristics, as well as its relationship to the processes of design activity. This study aims to identify and organize the key attributes of abductive reasoning and to elucidate its role in architectural design practice. The research adopts a qualitative approach based on thematic analysis and employs a systematic review following a seven stage protocol. The research corpus initially consisted of 46 sources retrieved up to August 2025 from three databases—Web of Science, Scopus, and ScienceDirect. After quality appraisal and the removal of duplicates, 14 journal articles and one book chapter were selected for analysis. The data were examined through coding and interpretive thematic analysis. The findings resulted in a cyclical conceptual model comprising five interrelated conceptual clusters: the nature of abductive reasoning; activation contexts and triggers; cognitive mechanisms; operational strategies; and individual characteristics and outcomes. The results indicate that abductive reasoning is activated when designers encounter ambiguity. Through processes such as framing and visualization, it progresses toward conjectural testing and reflective evaluation, ultimately leading to sensemaking, holistic understanding, innovation, and originality in design practice.