Many minimally invasive thermal techniques, such as radiofrequency ablation, laser ablation, and microwave ablation (MWA) have gained substantial attention and broad clinical acceptance for the treatment of several tumors. All these treatments cause a high temperature increment, cytotoxic for the cells within the target organ. The knowledge of the ablation process effects in terms of temperature increment can be crucial to optimize the treatment settings and to avoid the occurrence of damages the healthy structures located around the tumor. During the last years, several feasibility studies on the use of MWA for bone tumor have been carried out, but an experimental analysis of the temperature reached within the bone during the treatment has not been performed. The aim of this work is to present a multi-point temperature measurement reached within the bone during MWA. Experiments were performed on an ex vivo bovine femur using a MWA system at a power of 75 W and a treatment time of 8 min. Femur temperature was measured in 30 points inside the bone and around the MW antenna, covering a large area. The measurements were performed by using three fiber optics embedding 10 fiber Bragg grating sensors each. Results of this pilot study showed the capability of the proposed approach for a multi-point temperature monitoring in bone undergoing MWA. Together, these experiments represent the first step towards the design of a system capable of understanding the effects of MWA on bone tumors, to rationally define the best MWA settings for the treatment of a specific tumor, and so to improve the treatment outcomes in this promising clinical application.