Borates are well known for their ability to protect wood against fungal and insects attacks. However, their use in outdoor applications is limited due to their high leachability from treated wood. In this study, monoglycerides were investigated as fixative agents to reduce boron depletion from Scots pine using a double vacuum impregnation process involving impregnation with disodium octaborate tetrahydrate (DOT) followed by a second impregnation with the fixative agent. Significant reduction in boron leachability in samples treated with monoglycerides was observed compared to the standalone boron treated specimens. Evaluation of decay resistance of treated blocks using the brown rot fungus Poria placenta indicated a slight increase of durability, while resistance to termites attacks was strongly improved as demonstrated by the low weight losses and the high termites mortality levels observed. Monoglycerides could therefore be valuable additives to reduce boron depletion for outdoor applications in which wood is exposed to natural leaching conditions.