The suffix ‘-gɑr’ is a nominal and adjectival suffix in Persian which is believed by most researchers to express the subjective (agentive) meaning. The purpose of the present research is to explore this suffix within the framework of two theories of Construction Morphology and Cognitive Grammar in order to provide a cognitive and constructional account of the formation of words with this suffix. Empirically, the paper adopts a corpus-based method and theoretically, it adopts a cognitive and constructional approach. The data include a corpus of 29 derivational words having the suffix ‘-gɑr’ extracted from the authors’ own morphological corpus (including more than 10000 complex words) and Farhang-e Zansoo (Reverse Dictionary, Keshani 1993). The results of the research reveal that the suffix ‘-gɑr’ can appear in six different constructional subschemas to express the cognitive domains of agenthood, voice and relation. The results also show that the two cognitive process of construal and categorization have crucial roles in the formation of these constructional subschemas and the semantic category of the suffix ‘-gɑr’.