We analyse the top 20 emerging issues in bioengineering, identified through a horizon scan. This follows on from the 2017 transatlantic bioengineering horizon scan. We drew on 38 bioengineering experts across science, technology, security and policy from 13 countries using a modified Delphi technique. Participants provided an initial list of 83 issues that were scored according to their potential impact, plausibility and novelty. A shortlist of 40 issues were then discussed in a workshop and anonymously re-scored. The resulting 20 highest-scoring issues span topics in political economy (the regulation of genomic data, increased philanthropic funding and malicious uses of neurochemicals) through to environment (crops for changing climates and agricultural gene drives) and medicine (replacement organs and personalised medicine). These advances in bioengineering could have substantial positive and negative global impacts. Early identification of such developments and issues is of critical interest to researchers, policy-makers and the wider public.