Mental health is largely shaped by the daily environments in which people live their lives, with positive components of mental health emphasising the importance of feeling good and functioning effectively. Promoting mental health relies on broad-based actions over multiple sectors, which can be difficult to measure. Different types of Impact Assessment (IA) frameworks allow for a structured approach to evaluating policy actions on different levels. A systematic review was performed exploring existing IA frameworks relating to mental health and mental wellbeing and how they have been used. A total of 145 records were identified from the databases, from which 9 articles were included in the review, with a further 6 studies included via reference list and citation chaining. Five different mental-health-related IA frameworks were found to be implemented in a variety of settings, mostly in relation to evaluating community actions. A Narrative Synthesis summarised key themes from the 15 included articles. Findings highlight the need for participatory approaches in IA, which have the dual purpose of informing the IA evaluation and advocating for the need to include mental health in policy development. However, it is important to ensure that IA frameworks are user-friendly, designed to be used by laypeople in a variety of sectors and that IA frameworks are operational in terms of time and monetary resources.