Beaches and coastal dunes are fragile ecosystems providing critical biodiversity and ecosystem services, yet increasingly threatened by climate change and intensive tourism. Effective large-scale monitoring is essential to safeguard both ecological and socio-economic values. We developed and tested a community (citizen) science-based monitoring protocol through the ‘Guardiani della Costa’ project (Italy), engaging secondary school students through structured training and teamwork-based field surveys for standardized assessments of beach and dune naturalness. The protocol focuses on the most dynamic and sensitive portion of the littoral system and uses simple indicators, such as beach width, sediment coarseness, dune presence, erosion signs, backshore line typology and key indicator plant species across 10 sampling points per site. Data reliability was assessed through GIS analyses and statistical comparisons between student observations and expert evaluations. High agreement was found for most parameters, and specific limitations related to coordinates and species detection were identified. The results demonstrate that structured community science can generate reliable, spatially extensive ecological data suitable for large-scale assessments of beach and dune naturalness. Practical implications. The protocol offers a cost-effective, scalable tool to monitor coastal dune health, identify beaches potentially vulnerable to erosion or human disturbance, prioritize sites for detailed investigation and support coastal management actions such as dune restoration, visitor pressure mitigation and conservation planning, including applications relevant to Habitat Directive and the Littoral Active Zone concept. © 2026 The Author(s). Ecological Solutions and Evidence published by John Wiley & Sons Ltd on behalf of British Ecological Society.