Background. Everyday sadism is unique among the dark personality traits that form the Dark Tetrad. Whilst it shares the Dark Core of Personality with psychopathy, narcissism, and Machiavellianism, it is theoretically distinct from the other members in that involves an appetite for cruelty. Objective. Given mounting evidence of everyday sadism being associated with socially aversive behaviour, and its potential utility in predicting harmful behaviour within the general population; the current review examined the relationship between sadism and aggressive behaviour. Data sources. Seven well-established electronic bibliographic databases and two other sources were systematically searched. Supplementary searches were employed. Study selection. The initial search identified 627 full-text articles. Following application of inclusion and exclusion criteria, 39 full-text articles inclusive of 52 studies were subject to quality assessment. Data was extracted from 52 studies, with 48 studies eligible for quantitative synthesis. Data synthesis. Correlational analyses were the most common method of examining sadism and aggression. A multi-method approach was employed to standardize effect sizes into a common metric (correlation coefficient). A meta-analysis was conducted using 57 effect sizes from 48 studies with 22,179 participants, revealing a pooled correlation coefficient of 0.35 (95% CI = 0.29, 0.40). Significant heterogeneity was observed which warranted sensitivity and subgroup analyses. Conclusions. Overall, a moderate relationship was found between subclinical sadism and aggressive behaviour, as defined by acts ranging from verbal to physical, and sexual aggression and violence. A stronger, moderate relationship was found between sadism and perpetration of aggressive behaviour online, indicating that anonymity may unleash the darker side of personality within the general population. The implications of this finding are considered.