With increasing age and multimorbidity, medication regimens become demanding, potentially resulting in suboptimal adherence. Social support has been discussed as a predictor of adherence, but previous findings are inconsistent. The study examines general social support, medication-specific social support, and social conflict as predictors of adherence at two points in time (6 months apart) to test the mobilization and social conflict hypotheses. A total of 309 community-dwelling multimorbid adults (65-85 years, mean age 73.27, 41.7% women; most frequent illnesses: hypertension, osteoarthritis and hyperlipidemia) were recruited from the population-representative German Ageing Survey. Only medication-specific support correlated with adherence. Controlling for baseline adherence, demographics, physical fitness, medication regimen, and attitude, Time 1 medication-specific support negatively predicted Time 2 adherence, and vice versa. The negative relation between earlier medication-specific support and later adherence was not due to mobilization (low adherence mobilizing support from others, which over time would support adherence). Social conflict moderated the medication-specific support to adherence relationship: the relationship became more negative, the more social conflict participants reported. Presence of social conflict should be considered when received social support is studied, because well-intended help might have the opposite effect, when it coincides with social conflict.