Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions. BACKGROUND: Paediatric dog bites are a significant public health problem worldwide. Existing prevention programmes focused on altering children's risky behaviour with pet dogs tend to be atheoretical and only moderately effective. OBJECTIVE: Test efficacy of a website to train young children in relevant cognitive skills to be safe with pet dogs in their home. SETTING: Birmingham, Alabama, USA. METHODS: A randomised trial will be conducted with an expected sample of two groups of 34 children (total N=68) ages 4-6 years. One group will engage in the newly designed website at home for 2 weeks and the other group will engage in a control website on transportation safety for an equivalent amount of time. All participants will complete a battery of laboratory-based tests to assess safety with dogs and cognitive functioning at baseline and postintervention. OUTCOME MEASURES: Primary analyses will be conducted through linear mixed models testing change over time. Children's cognitive functioning, knowledge about safety with dogs, and behaviour with dogs in simulation and in vivo will serve as the primary outcomes. CLINICAL TRIAL REGISTRATION: This study is exempt from registry at the US government website, http://www.clinicaltrials.gov, based on being a behavioural trial in the early phases of testing.