Language is used to talk about the world, typically structured in sentences that consist of a topic (subject) and a comment (predicate). The main verb, as the head of the predicate, is the most important part of a sentence as it determines the presence of role players in the sentence as its arguments. Different verbs require various numbers and types of arguments with specific thematic roles. Each verb in a sentence, therefore, assigns thematic roles to its arguments and this forms the argument structure of a language as a language universal property. Kisa, a Bantu language spoken in Western Kenya, has an argument structure that is unique to itself because each language has its own specific way of presenting and realising language universal properties. However, the argument structure of Kisa has not been described and documented. Using a descriptive analytic research design, adopting the valency theory and basing on data collected from two native speakers and verified by the author as a native speaker of Kisa, this paper describes the argument structure of Kisa and shows that Kisa verbs allow up to 3 arguments in a sentence assigned specific thematic roles such as agent, patient, and experiencer. The morphology-syntax-semantic inter-phase is shown to be at play, in Kisa, where prefixes participate in the determination of the argument structure of verbs and assignment of thematic roles. These findings contribute to a deeper understanding of Kisa's linguistic structure and its implications for valency theory in Bantu languages.