BEAM Exchange began the practitioner-led research initiative to support innovation by groups of practitioners who face common challenges in exploring how connections could be built between existing groups of practitioners and researchers or specialists. This research brief captures the experience of one group of practitioners interested in integrating knowledge on social norms from fields outside of market systems into their work on identifying and measuring systemic change. The group includes representatives from MarketShare Associates (MSA), CARE International, Habitat for Humanity International, ACDI/VOCA and Mesopartner. The social norms specialists are Ben Cislaghi from the London School of Hygiene & Tropical Medicine and Holly Shakya from the University of California San Diego. This research brief outlines key ideas from social norms theory and explores implications for research and implementation by market systems development (MSD) programmes. It is meant to help programme teams grasp the social norms at play in their current situation so they can factor them into intervention design and iteration by monitoring the impacts of their interventions.