Nootka and Ditidaht (Nuu-chap-nulth), which belong to the Southern Wakashan branch of the Wakashan language family, exhibit complex properties with respect to glottalization. Although they have the same phoneme inventory, these two sister languages have different results in glottalization depending on manners of articulation of the affected consonant. Also, their glottalization is sensitive to morphological categories. The triggering factor of glottalization is a suffix with a glottal in its initial position, and the aspects of glottalization are different depending on the morphological category of the suffix in question, lexical or grammatical. These two properties in terms of glottalization in Nuu-chah-nulth: language variation and interaction between phonology and morphology, will he treated in Optimality Theory in this paper.