This preliminary study investigated the impact of the online interactive programme Brainology (which aimed to encourage a growth mindset) on the mindset, resiliency and sense of mastery of secondary school pupils. A quasi-experimental pre-, post- and follow-up mixed-methods study was carried out with 33 participants aged 13-14 years. The measures were Dweck's theories of intelligence scale and Prince-Embury's resiliency scales for children and adolescents. Quantitative data were analysed using analysis of variance. Qualitative data from focus groups were categorised and coded. The programme led to a significant increase in pre- to post-mindset scores for the intervention group. However, there was a significant decline at follow-up and the initial impact of the intervention was not sustained. There were no significant changes in mindset for the comparison group. There were no significant changes in resiliency or sense of mastery for either group. The significant short-term impact of Brainology and non-significant follow-up findings are discussed. The present study has limitations such as small sample size, which has implications for generalisability. Future research should investigate the longer term effectiveness of educational interventions in schools.