Nonribosomal peptide synthetases (NRPSs) catalyze the formation of complex peptide natural products, of which many display therapeutically useful activity. Conventional NRPSs have been characterized as modular and co-linear assembling. Recent studies of many NRPS systems revealed some examples where the catalytic logic does not directly correspond to the linear arrangement of modules and domains. This mini review summarizes the recently discovered NRPS biosynthetic pathways focused on four types of unconventional assembling ways including iterative NRPSs, nonlinear NRPSs, module skipping NRPSs and the nonribo-somal propeptide biosynthetic mode.