Abstract The present article is dedicated to the syntax, morphology, and phonetics of ideophones in Arusa Maasai. After examining the compliance of 69 ideophonic lexemes with the typologically driven prototype of an ideophone, the authors conclude that Arusa ideophones may range from canonical to non-canonical even within a single language module. When syntax, morphology, and phonetics are considered jointly, holophrastic and asyntagmatic ideophones are more canonical than ideophones used as verbal modifiers and parts of complex predicates, which are, in turn, more canonical than predicative ideophones. The extent of canonicity is inversely correlated with the systematicity and integration of ideophones in sentence grammar and their diffusion into other lexical classes: predicative ideophones have been fully incorporated into the category of verbs; for ideophones employed as verbal modifiers, a comparable incorporation into the category of adverbs has not been completed; for all the other types, especially holophrastic and asyntagmatic, ideophones still maintain their categorical individuality. Overall, ideophones constitute an “old” category in Arusa, one that is well advanced on its grammaticalization cline.