This book constitutes the refereed proceedings of the 25th International Conference on DNA Computing and Molecular Programming, DNA 25, held in Seattle, WA, USA, in August 2019. The 12 full papers presented were carefully selected from 19 submissions. The papers cover a wide range of topics relating to biomolecular computing such as algorithms and models for computation on biomolecular systems; computational processes in vitro and in vivo; molecular switches, gates, devices, and circuits; molecular folding and self-assembly of nanostructures; analysis and theoretical models of laboratory techniques; molecular motors and molecular robotics; information storage; studies of fault-tolerance and error correction; software tools for analysis, simulation, anddesign; synthetic biology and in vitro evolution; and applications in engineering, physics, chemistry, biology, and medicine.