Spending time alone in nature has been found to benefit well-being, but the mechanisms underlying this relation are understudied. The current study validated an assessment of the construct of connectedness to nature in solitude (CNIS) and evaluated a model linking CNIS, time spent alone in nature, and indices of well-being. Participants were N = 812 emerging adults (Mage = 19.45, SD = 1.87) attending university in southeastern Ontario, Canada. Participants completed a series of self-report measures assessing CNIS, time alone in nature, affinity for solitude, nature connectedness, loneliness, aloneliness, and life satisfaction. Factor analysis of the 7-item CNIS Scale indicated a one-factor solution. Regression analyses indicated that at low levels of CNIS, time alone in nature was significantly and positively related to loneliness and aloneliness, but at higher levels of CNIS, this relation was attenuated. The current study provides initial evidence for the importance of CNIS as a moderator of the links between time alone in nature and well-being.