We have in this work entitled "Etude de la catégorie adjective en français et en jju" examined the adjectives of two languages which are from different background: French and Jju. French being a roman language from indo-European family and Jju, an African language from the Niger Congo lineage. The problem advanced by the study is that minority languages have been neglected in the area of linguistic research and this could lead to their extinction. In realizing this work, a structuralist approach was adopted. This study therefore, aims at promoting such languages not to allow them go into extinction. This study has shown that there are many similarities and dissimilarities in the adjectives of the two languages. The French adjectives vary in gender and in number and that of jju vary only in number. The position of French qualitative adjective is variable as it is sometimes found before and after the noun. While in jju, the qualitative adjective is found always before the noun. Concerning their similarity, the adjectives of these languages play vital role in qualifying and determining an object. Finally conclusions are drawn that although the adjectives are present in the two languages, the concept is unique for each language because the principles and characteristics vary in each language.