Efficient social interaction is essential for an adaptive life and consists of sequential processes of multisensory events with social counterparts. Social touch/contact is a unique component that promotes a sequence of social behaviors initiated by detection and approach to assess a social stimulus and subsequent maintenance of touch/contacts to form prosocial relationships. We hypothesized that the thalamic sensory relay circuit from the posterior intralaminar nucleus of the thalamus (pIL) to the paraventricular nucleus of the hypothalamus (PVN) and the medial amygdala (MeA) plays a key role in the social contact-mediated sequence of events. We found that neurons in the pIL along with the PVN and MeA, were activated by social encounters, and that pIL activity was more abundant in a direct physical encounter, whereas MeA activity was dominant in an indirect via grid encounter. Chemogenetic inhibition of pIL neurons selectively decreased the investigatory approach and sniffing of a same-sex, but not an opposite-sex, stimulus mouse in an indirect encounter situation and decreased the facial/snout contact ratio in a direct encounter setting. Furthermore, chemogenetic pIL inhibition had no impact on anxiety-like behaviors or body coordinative motor behaviors, but it impaired whisker-related and plantar touch tactile sense. We propose that the pIL circuit can relay social tactile sensations and mediate the sequence of non-sexual prosocial interactions using an investigatory approach through tactile contact.