Methods to capture the complexity of using policy instruments would allow us to better evaluate the reasons for their effectiveness. Drawing from complexity science, we produce a Causal Loop Diagram to analyse the implementation of two informational policy instruments in a tourism destination: the Global Sustainable Tourism Council criteria and the European Tourism Indicator Scheme. To interpret the emerging system structure, we use complexity theory concepts of emergence; interdependence and interconnectivity; co-evolution; self-organisation; feedback; historicity and path dependence. This qualitative methodology sheds light on the interplay of factors that facilitate and impede the continuous use of these policy instruments. It shows how adopting a complexity science approach to evaluation studies can be invaluable to making tourism policy interventions more impactful.