The aim of this paper is twofold. On the one hand, it gives a systematic description of adverbials in Tsou. On the other, it illustrates how adverbials are syntactically represented and derived in Tsou. Two types of adverbial constructions can be identified. In one type, adverbials are realized as adverbial verbs and situated between a temporal/modal auxiliary and a lexical verb, and they take the prefixes a-/i'-. In the other type, adverbials occur as bound roots and combine with an event-denoting lexical prefix, yielding an adverbial compound. It is argued that adverbial verbs are generated as functional heads above Voice/vP, whereas adverbial compounds are generated as lexical heads under Voice/vP. This analysis accounts for a number of otherwise puzzling asymmetries, including the following: (i) an adverbial compound can stand alone and take nominal arguments but an adverbial verb cannot; (ii) an adverbial compound can be marked for Locative Voice and Referential Voice but an adverbial verb cannot; (iii) the root of an adverbial compound is restricted to event adverbials, but the root of an adverbial verb is free from this restriction; (iv) the prefix of an adverbial compound can be voice-marked, but the prefix of an adverbial verb is invariant; and (v) adverbial verbs must precede adverbial compounds, not the other way around.