This study tested whether age moderates the longitudinal relationships between upward and downward comparisons on Instagram and three identity processes (i.e., commitment, in-depth exploration, and reconsideration of commitment). Two hundred and eleven British emerging adults completed two self-report surveys, two months apart, in early 2020. A cross-lagged panel model with interaction terms found that age moderated the relationships between both upward and downward comparisons on Instagram and commitment. Contingent moderations were found: the relationship between upward comparisons and commitment was negative for older participants, whilst the relationship between downward comparisons and commitment was negative for younger participants. Significant age differences were not found in the paths between the comparison behaviours and the two exploratory processes. Findings therefore provide evidence to suggest that developmental factors may inform the identity implications of social comparisons on Instagram during emerging adulthood, and thus, developmental sensitivity is required when supporting emerging adults to navigate the platform.