The postnatal period confers a high risk for anxiety in women, but few life stage-specific resources are available. This is despite public health policy recommendations for universal screening for mental health problems. Using the first two steps of the four-step United Kingdom Medical Research Council (UKMRC) guidance and with input from consumers, we developed and piloted a supported self-help psychoeducation resource for the management of syndromal or subsyndromal generalised postnatal anxiety. The theoretically sound What Am I Worried About (WAWA) resource uses cognitive behaviour therapy and mindfulness in a seven-module programme supported by a 30-min telephone consultation with a mental health professional during each module. Results of an open pilot confirm acceptability, safety, non-stigma, feasibility and preliminary efficacy. Subject to successful completion of Step 3 of the UKMRC guidance, WAWA can be provided for anxiety management to women in a stepped-care model in primary postnatal health services.