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There are significant environmental benefits of understanding the water characteristics in engineered wood products as it is related to their fungi/mold susceptibility. The primary goal of this investigation was to gain a fundamental understanding of the water characteristics in oriented strandboard (OSB) using magnetic resonance (NMR) approaches. Isotherm sorption tests were conducted on commercial OSB panels made from different wood type and adhesive combinations. Moisture content (MC) determination, water activity (aw) measurement, and magnetic resonance relaxometry plus Distributed Exponential Analysis were performed on the OSB specimens during isotherm sorption tests. The results showed that neither MC nor aw is a reliable indicator of mold susceptibility of OSB. NMR relaxometry together with chemometric analysis detected that the state of water with the longest spin-spin relaxation time is responsible for the mold susceptibility of OSB. OSB made from pine had higher mold susceptibility than that from aspen because the pine OSB had a third water component with very long spin-spin relaxation time. The results suggest that new protocol for quality control in OSB production based on MR relaxometry could replace the current moisture content measurement.