This paper investigates ideophones and interjections, and their correlation with sound symbolism, in Seediq, an Austronesian language spoken in central and eastern Taiwan. Ideophones are categorized as onomatopoeic and depictive, and interjections as expressive, conative, and phatic. In terms of structure, most ideo-phones are characteristic of a CVC syllable with optional reduplication, which is not the case for interjections. Although both ideophones and interjections may function as verbal predicates, only ideophones allow for inflections or derivations. The paper also explores the correlation of ideophones and interjections with imitative, corporeal, synesthetic, and conventionalized sound symbolism. Synesthetic sound symbolism is manifested by the Seediq vowels, with/i/for diminution,/a/for augmentation, and/u/for roundness. Several phonesthemes representing conventionalized sound symbolism are also identified.