DNA computing has attracted attention as a tool for solving mathematical problems due to the potential for massive parallelism with low energy consumption. However, decoding the output information to a human-recognizable signal is generally time-consuming owing to the requirement for multiple steps of biological operations. Here, we describe simple and rapid decoding of the DNA-computed output for a directed Hamiltonian path problem (HPP) using nanopore technology. In this approach, the output DNA duplex undergoes unzipping whilst passing through an α-hemolysin nanopore, with information electrically decoded as the unzipping time of the hybridized strands. As a proof of concept, we demonstrate nanopore decoding of the HPP of a small graph encoded in DNA. Our results show the feasibility of nanopore measurement as a rapid and label-free decoding method for mathematical DNA computation using parallel self-assembly.