Abstract: Estrogen receptor alpha (ERα) is an important molecular target for the diagnosis and endocrine therapy of breast cancer. BHPI is a recently identified class of novel non-steroidal ERα-targeting small molecules; however, no studies on its radiolabeling or molecular imaging applications have been reported to date. In this study, a boronic ester precursor of BHPI (B-BHPI) was designed and synthesized, and the PET molecular probe ¹⁸F-BHPI was successfully prepared via a copper-mediated nucleophilic radiofluorination strategy. The radiochemical properties, in vitro stability, cellular uptake characteristics, and in vivo biodistribution of the probe were systematically evaluated. The results showed that ¹⁸F-BHPI was obtained with a radiochemical conversion (RCC) of (37.75±7.39)%, a radiochemical yield (RCY) of (6.28±0.15)%, a radiochemical purity (RCP) of (96.38±1.62)%, and a molar activity of (0.29±0.11) GBq/μmol. The LogP value was 1.10±0.27. The probe exhibited excellent stability in both saline and mouse serum, remaining predominantly intact after 240 min of incubation. Cellular uptake studies demonstrated significantly higher accumulation of ¹⁸F-BHPI in ERα-positive MCF-7 cells than in ERα-negative MDA-MB-231 cells. Competitive inhibition experiments further revealed that tamoxifen, 17β-estradiol, and BHPI markedly reduced probe uptake in MCF-7 cells, with BHPI showing the strongest blocking effect. Biodistribution studies in normal female SD rats indicated that ¹⁸F-BHPI was mainly metabolized through the hepatobiliary and intestinal pathways and displayed a well-defined in vivo distribution and clearance profile. To the best of our knowledge, this study represents the first successful radiolabeling of BHPI and the first construction of a BHPI-based molecular imaging probe. The resulting ¹⁸F-BHPI exhibited favorable physicochemical properties and ERα-related uptake characteristics, providing a useful tool for in vivo tracing of BHPI and a promising foundation for the development of novel ERα-related PET molecular probes.