In two visual word eye tracking studies, we investigated the influence of prosody and case marking on children’s and adults’ thematic role assignment. We assigned an SVO/ OVS-biasing (vs. neutral) prosodic contour to unambiguously case marked German subject-verb-object (SVO) and object-verb-subject (OVS) sentences respectively. Scenes depicted ambiguous action events (e.g., donkey-paints->elephant-paints->cheetah) but case marking and prosody could, in principle, disambiguate. In adults, case marking but not prosody rapidly guided thematic role assignment. Children did not rely on case marking but exploited the biasing prosody to enhance their agent-first interpretation of the sentences. These results suggest that in scenes depicting fully ambiguous role relations, children’s understanding of case marking at the age of five is not yet robust enough to enable thematic role assignment. Prosody did not overwrite the SVO preference, it rather enhanced it.