Objectives: Maintaining offline social participation (i.e. face-to-face social interaction) is key for healthy aging, but older adults who experience pain tend to restrict their social activity outside of the home. The onset of pain may set off a downward spiral where lowered social participation increases the risk of depression and vice versa. This study thus assesses whether online social participation (i.e., the use of online social network sites) moderates the effect of pain on depression, possibly functioning as a compensatory mechanism for reduced offline social participation for those in pain. Method: Logistic regression models with a lagged dependent variable were used with panel data from the National Health and Aging Trends Study. An interaction term was included to assess the moderating effect of online social participation. Results: We find that online social participation buffers the detrimental effect of pain on depression. However, the effect of pain on online social participation was not statistically significant. Discussion: Findings show that online social participation can alleviate the negative effects of pain on mental well-being, and suggest that online social participation can supplement attempts to maintain offline social participation in later life, especially for those whose social activity may be limited by pain.