Recent event-related potential studies report a P600 effect to incongruous verbs preceded by semantically associated inanimate noun–phrase (NP) arguments, e.g., “eat” in “At breakfast the eggs would eat…”. This P600 effect may reflect the processing cost incurred when semantic–thematic relationships between critical verbs and their preceding NP argument(s) bias towards different interpretations to those dictated by their sentences’ syntactic structures. We have termed such violations of alternative thematic roles, ‘thematic role violations.’ Semantic–thematic relationships are influenced both by semantic associations and by more basic semantic features, such as a noun’s animacy. This study determined whether a P600 effect can be evoked by verbs whose thematic structures are violated by their preceding inanimate NP arguments, even in the absence of close semantic–associative relationships with these arguments or their preceding contexts. ERPs were measured to verbs under four conditions: (1) non-violated (“At breakfast the boys would eat…”); (2) preceded by introductory clauses and animate NPs that violated their pragmatic expectations but not their thematic structures (“At breakfast the boys would plant…”); (3) preceded by semantically related contexts but inanimate NPs that violated their thematic structures (“At breakfast the eggs would eat…”); (4) preceded by semantically unrelated contexts and inanimate NPs that also violated their thematic structures (“At breakfast the eggs would plant…”). Pragmatically non-thematic role violated verbs preceded by unrelated contexts and animate NPs evoked robust N400 effects and small P600 effects. Thematically violated verbs preceded by inanimate argument NPs evoked robust P600 effects but no N400 effects, regardless of whether these inanimate arguments or their preceding contexts were semantically related or unrelated to these verbs. These findings suggest that semantic-thematic relations, related to animacy constraints on verbs’ arguments, are computed online and can immediately impact verb processing within active, English sentences.