Purpose: This study aims to examine a structural relationship among agreeableness, similarity in agreeableness, positive affect and transfer of informal learning. Also, it investigates the mediating role of motivation. Design/methodology/approach: Data were collected by a survey via snowball sampling. In total, 742 respondents at 72 companies from multiple industries in South Korea participated. The authors performed exploratory confirmatory factor analyses and structural equation modeling to test the research model and hypotheses. Findings: The results showed that agreeableness made a dual impact as a personal and a relational trait enhancing the employee's positive affect, and motivation to learn fully mediated the relationship between agreeableness and transfer of informal learning. This supports that prosocial personality traits enhance the employee's motivation, learning and learning application. The full mediation of motivation to learn between positive affect and informal learning transfer emphasizes the importance of intentionality on the part of employees in informal learning contexts. Originality/value: Organizational research pays little attention to social perspectives of informal learning (Varela et al., 2011). The results highlight that workplace informal learning is a socio-psychological process; thus, examining social and psychological factors together would be beneficial.