Reflecting the increasing interest in connectedness to nature (CN), research on connectedness to humanity (CH) has surged. Currently, the focus is on investigating the interplay and distinct contributions of CH and CN; however, the lack of a validated tool for assessing CH has led researchers to use non-comparable scales. This paper aims to (1) validate the Connectedness to Humanity Scale, adapted from the Connectedness to Nature Scale, (2) identify a global factor of connectedness underlying both CH and CN, and (3) delineate their unique contributions. Study 1 (N = 188) and Study 2 (N = 187) confirmed the unidimensional factor structure of the adapted scale and established its convergent and divergent validity, demonstrating its strong psychometric properties. Using bi-factor exploratory structural equation modeling, Study 3 (N = 311) identified the global ‘connectedness’ factor model underlying both the CH and CN scales as the best fit. Additionally, Study 3 isolated the unique contributions of CH and CN to mental health indicators (i.e., depressive symptoms, identity threat appraisal) and mindfulness measures (i.e., five facets of mindfulness, nonattachment, and authentic happiness). Multiple regression analyses revealed CH’s unique contributions to mental health indicators, nonattachment, and authentic happiness, while CN uniquely influenced the observing and non-reacting facets of mindfulness. Although both CH and CN are underpinned by a global factor, they remain distinct constructs that contribute differently depending on the context, underscoring the need to explore both simultaneously.