This paper is a morpho-semantic study of olfactory terms and linguistic expressions for describing odor in four Formosan languages, including Kavalan, Truku Seediq, Paiwan, and Thao, based on the author’s firsthand data. It shows that apart from very limited olfactory terms, reduplication is the most common means for manifesting the meaning of ‘(having) a smell / an odor of X’ in these languages. The formation usually involves a prefix which is found similar in these languages, in Kavalan as su-, Truku Seediq as s-, Paiwan as sa-, and Thao as tu-. Two parameters are taken into consideration: first, the selective restriction on the relevant lexical items for the reduplicative construction, and secondly, the reduplicative patterns in each language. It is proposed that the reason why odor is manifested by reduplication is due to its association with both iterative aspects and plurality. Having a smell is a continuing process, and it is mentally perceptible so that there should be enough entities in order to produce a persistent smell. Inspired by experimental studies in psychology on odor recognition and identification, which suggest a poverty of linguistic representation for odor perception, this paper discusses similarities and differences regarding how each language indicates such a meaning, as well as the semantic implications drawn from the comparison.