Individuals should alter when they socially associate with conspecifics to avoid potentially costly interactions. Moreover, individuals may vary in their propensity to use information about conspecifics when making such social decisions. However, surprisingly little is known about either the determinants of, or individual variation in, such ‘social plasticity’. We show here that eastern water dragons (Intellegama lesueurii lesueurii) may simultaneously use information from different components of their social environment when deciding whether or not to socially associate. In particular, we found that individuals altered when they socially associated according to levels of potential conflict and competition in their social environment; both sexes socially associated more at higher local density than would be expected under increased random encounters. Further, females were more likely to socially associate during the breeding season, and when there were more males and/or conspecifics whom they typically avoided in their social environment. This suggests that females may seek safety in numbers when the potential for intra-sexual conflict or sexual harassment is high. Using a behavioural reaction-norm framework, we also provide novel evidence to show that individuals vary in the extent and direction of their social plasticity, and that males varied more than females. Our study thus implies that individuals use multiple cues in their environment when deciding to socially associate, and that the resulting social plasticity varies between the sexes and between individuals.