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A 45-year-old female complained of a right breast mass for 1 month. Ultrasound-guided breast biopsy confirmed invasive ductal carcinoma. The patient underwent [18F]FDG PET/CT for tumor staging and was included in a clinical trial of [68 Ga]Ga-FAPI (NCT04499365). Written informed consent was obtained from the patient. In [18F]FDG (a–b) and [68 Ga]Ga-FAPI PET/CT (c–d), the primary lesions (black arrow) of the right breast and the right axillary metastatic lymph nodes (black dotted arrow) showed high radioactivity uptake. No increased uptake of the tracers and abnormal bone mineral density were found in the right ilium and acetabulum (g). However, the abnormally increased uptake was observed in the right ilium and acetabulum with [99mTc] MDP SPECT/CT (e–f). The patient subsequently underwent a needle biopsy of the right iliac lesion, which was pathologically confirmed to be a bone metastasis from breast cancer (h). In this case, underlying the combination of negative FDG PET and CT findings, and positive MDP findings, it is rational to think that the lesion might be an early osteogenic bone metastasis. It has been reported that FDG uptake in osteoblastic bone metastases may not be obvious [1, 2], while MDP uptake is significantly increased. [68 Ga]GaFAPI serves as a promising radiotracer for the assessment of solid tumors [3, 4]. However, this present case is the first study to reveal that [68 Ga]Ga-FAPI might have false negative results in detecting bone metastasis. The reason might be the low expression of FAPI in early bone metastasis. Therefore, the value of [68 Ga]Ga-FAPI in bone metastases requires further investigation.