Typological classification of languages according to suprasegmental systems recognizes pitch-accent, tonal, or/and stress systems. Although almost all Bantu languages are tonal, there are those that show stress systems only, those that show tone and penult lengthening systems and those that show contrastive penult and final prominence, portraying ambiguous systems. Prominence as a feature of language manifests itself in languages in terms of metrical structure, prosodic structure and linguistic stress assignment. The phenomenon of linguistic stress, in Bantu languages, is controversial. It has been argued that most present-day Bantu languages do not depict linguistic stress distinctions and patterns. Instead, they show pitch-accent distinctions culminating into tonal distinctions and patterns. Kisa, a Bantu language spoken in Western Kenya, portrays a mixed system of tone and stress. Given that linguistic stress has not been given much attention in the analysis of Bantu languages, this paper describes and analyses the stress patterns of Kisa words in Optimality Theory (OT). It employs a descriptive design and bases on data generated by two native speakers of Kisa and verified by the author as a native speaker of Kisa. The findings show that Kisa exhibits linguistic stress patterns that are weight sensitive. There is one primary stress per word; primary stress falls on the penultimate syllable or the rightmost heavy syllable in a word. Secondary stress falls on the left mora in a foot marked from the right to the left of the word. The findings attest to the fact that Kisa portrays a mixed system of stress and tone. But because tone height and vowel duration do not always co-occur and in Kisa and that Kisa portrays a weight sensitive stress system, duration is the primary phonetic correlate of stress in this language, even though loudness and pitch are also correlates of stress in Kisa.