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Background: Studies in prospective cohorts have suggested that enterovirus infections are associated with the appearance of islet autoantibodies that precede later appearance of type 1 diabetes (T1D). It was shown that in addition to an antibody‐mediated anti‐coxsackievirus (CV)‐B neutralizing activity of serum from patients with T1D, there was also enhancing anti‐CV‐B activity in vitro. In this study, the patterns of enhancing and neutralizing anti‐CV activities were analysed from consecutive serum samples collected from children who were followed from birth until they developed T1D in the Finnish Type 1 Diabetes Prediction and Prevention (DIPP) study and compared to those in non‐diabetic control children. Methods: The titres of serum neutralizing activity were analysed against those CVs which were detected in the stools in these children (CV‐B3, CV‐B5 or CV‐A4) using plaque assay. The enhancing activity of these serum samples was analysed by measuring interferon‐alpha (INF‐α) production in cultures of peripheral blood mononuclear cells (PBMC) inoculated with a mixture of these viruses and diluted serum. Results: A sustained anti‐CV enhancing activity was observed in consecutive serum samples in patients with T1D. The pattern of responses differed between children who developed T1D and control children. In patients, the anti‐CV enhancing activity was predominant or even exclusive over the neutralizing activity, whereas in controls the enhancing and neutralising activities were more balanced or the neutralizing activity was largely predominant. Conclusions: Evaluating the anti‐enterovirus neutralizing and enhancing activity of serum samples can be useful to investigate further the relationship between enteroviruses and the development of T1D.