It is a fundamental human need to secure and sustain a sense of social belonging. Previous research has shown that individuals who are lonely are more likely than people who are not lonely to attribute humanlike traits (e.g., free will) to nonhuman agents (e.g., an alarm clock that makes people get up by moving away from the sleeper), presumably in an attempt to fulfill unmet needs for belongingness. We directly replicated the association between loneliness and anthropomorphism in a larger sample (N = 178); furthermore, we showed that reminding people of a close, supportive relationship reduces their tendency to anthropomorphize. This finding provides support for the idea that the need for belonging has causal effects on anthropomorphism. Last, we showed that attachment anxiety—characterized by intense desire for and preoccupation with closeness, fear of abandonment, and hypervigilance to social cues—was a stronger predictor of anthropomorphism than loneliness was. This finding helps clarify the mechanisms underlying anthropomorphism and supports the idea that anthropomorphism is a motivated process reflecting the active search for potential sources of connection.