Nackednaviruses and hepatitis B virus (HBV) have a common non-enveloped viral ancestor. While HBV acquired an envelope during evolution, nackednaviruses remained non-enveloped. Here, Pfister et al. apply CryoEM and NMR to characterize the capsid structure of African cichlid nackednavirus (ACNDV) at pH 5.5 and pH 7.5 and show that the capsid structure is very similar to that of HBV.