The idea that actions of people, organizations or governments may lead to Unintended Consequences (UICs) is not new. In health, UICs have been reported as a result of various interventions including quality improvement initiatives, health information technology implementation, and knowledge translation, especially those involving translation of broad policies (evidence-based medicine and patient-centred care) or system level improvement into actionable items or tools. While some unintended consequences cannot be anticipated, others may be predictable. In this article, we present a model based on cultural historical activity theory, which may help policy-makers, health leaders, and researchers better anticipate UICs resulting from implementation of new programs or technologies and take action to address them or mitigate their risk of occurrence. We support this model using examples of UICs of implementing family centred care principles, electronic health records, and computerized templates for quality improvement in chronic disease management.