Storytelling in face-to-face dialogue involves coordinating multiple modalities, including speech and gaze. When the addressee is a social robot rather than a human, narrators’ speech and gaze behavior may differ. However, few studies have examined both modalities within the same narratives, and it remains unclear how different aspects of multimodal behavior vary depending on whether the interaction partner is a social robot or a human. In this study, we examined how adults narrated picture-based stories to a social robot and a human interlocutor. Two modalities of narrative production were considered: pausing, separated into filled and unfilled pauses, and gaze behavior during the narration, directed either toward the story pictures or toward the listener. Critically, we examined whether shyness, considered as a continuous dimension of individual variation, relates to pausing and gaze behavior. Results revealed that speakers produced fewer filled pauses when narrating to the robot than to the human, while unfilled pauses did not differ. Additionally, higher shyness was associated with longer, though not more frequent, filled pauses in human-directed narration, although shyness did not reliably predict the magnitude of the partner effect. We discuss how our findings may contribute to a more nuanced understanding of multimodal interactions with embodied agents.