Our study explores workload and social support as two mechanisms that explain the cost-benefit interplay of organizational citizenship behaviors (OCBs) in relation to teachers’ work performance (WP) and maladaptive work outcomes (MWO, stress and burnout). We use a cross-sectional design to test the bright and dark sides of teachers’ OCBs with a sample of 2224 Romanian teachers (with an average age of 42.72 years old). Workload explains the association between OCBs, WP and MWO for high rather than low levels of OCBs, while social support explains the association irrespective of the OCB level. The association between OCBs targeted towards the organization, WP and MWO is mediated by workload, while the association between OCBs targeted towards individuals, WP and MWO is mediated by social support. Our results join the call for substantial social support offered to teachers and call for more refined and joint evaluations of the type and level of OCB that are conducive for teachers’ performance.