Abstract: Purpose: In South Africa, the field of scale development and utilisation in social work is referred to as ‘ecometrics’, i.e. the measurement of ecological constructs. There is, however, a lack of ecometric tools available for use by social workers, particularly in the area of measuring strengths or resilience. Given the high vulnerability of South African youth, this paper describes the design and validation of a youth resilience measure. Method: The Youth Ecological-Resilience Scale (YERS), a multidimensional, summated rating scale that measures youth resilience within an ecological framework, was designed and validated with a diverse sample of 575 young people, using ecometric techniques. Results: The YERS shows good levels of reliability and validity. Conclusions: The YERS is suitable for group administration and research, and also for assessment of individuals when triangulated with other assessment methods. Several studies of youth transitions using the YERS are described, as well as suggestions for its use in social work practice.