This thesis presents a linguistic description of the phonology and morphology of SIRIANO, an endangered Amazonian language traditionally spoken in the Vaupés River region of northwest Amazon, in Brazil and Colombia. There is little extant documentation of Siriano; therefore, the description is primarily based on the data gathered by the thesis chair Dr. Wilson de Lima Silva.Siriano is a typical Eastern Tukanoan language in terms of its typological characteristics. It has a relatively small phonemic inventory, and most of the phonemes, both vowels, and consonants have nasalized counterparts. The syllable structure is very simple. The glottal stop and fricative are phonetically realized in a careful speech to modify the syllable structure. Siriano has a two-tone system, with high and low tones. They can be lexical tones, but some of them are not and change accordingly with the morphological processes. Stress is also shown to interact with tone patterns. Nasal spreading is very commonly seen, but the oral inherent morphemes block this phonological process. It has plentiful nominal categories and noun-related suffixes, with simple morphological processes. Verbs require tense, aspect, modality, and evidential marking in the form of suffix attachment. Overt evidential marking is used to distinguish the present and distant past tense.