Pure Fe is implanted with B+in a target temperature range of −20–300 °C. The effects of the target temperature on the crystallinity and hardness of the B+‐implanted Fe are investigated. It is found that Fe2B is formed by using direct B+implantation into pure Fe at target temperatures ranging from −20 to 300 °C without subsequent annealing. ‘‘Cold‐implantation,’’ i.e., implantation at a lower target temperature, reduces crystallinity and increases the hardness of the B+‐implanted Fe. By contrast, increased target temperature produces B+‐implanted Fe with high crystallinity and relatively low hardness. Discussion focuses on how the target temperature during implantation affects the crystallinity of the B+‐implanted Fe from the standpoint of the recrystallization during implantation.