In this study we investigate the feasibility of detecting heavy neutral leptons (Nd) through exotic Higgs decays at the proposed International Linear Collider (ILC), specifically in the channel of e+e-→qqH with H→νNd→νlW→νlqq. Analyses based on full detector simulations of the ILD are performed at the center-of-mass energy of 250 GeV for two different beam polarization schemes with a total integrated luminosity of 2 ab-1. A range of heavy neutral lepton masses between the Z boson and Higgs boson masses are studied. The 2σ significance reach for the joint branching ratio of BR(H→νNd)·BR(Nd→lW) is about 0.1%, nearly independent of the heavy neutral lepton masses, while the 5σ discovery is possible at a branching ratio of 0.3%. Interpreting these results in terms of constraints on the mixing parameters |Eid|2 between SM neutrinos and the heavy neutral lepton, it is expected to have a factor of 10 improvement from current constraints.