Porous monetite is a promising material for bone graft applications because of its ability to balance resorption with new bone formation. However, the methods for fabricating porous monetite are very limited. In this study, a novel method for fabricating porous monetite was developed. Porous monetite grafts were successfully fabricated through the phase transformation of porous calcium sulfate anhydrate (CS) in sodium dihydrogen phosphate (NaH2PO4) solution under hydrothermal conditions at temperatures of 150 °C and 180 °C, denoted as PM-150 and PM-180, respectively. The results demonstrated that porous CS underwent a phase transformation, as evidenced by X-ray diffraction and SEM-EDX analysis, resulting in the formation of porous monetite. The diametral tensile strengths (DTS) of the resulting porous monetite groups were 0.45 ± 0.04 MPa and 0.41 ± 0.10 MPa for PM-150 and PM-180, respectively, comparable to that of the porous calcium sulfate precursor. The porous monetite obtained through this fabrication method had an average porosity of 50–60 %. They also demonstrated enhanced solubility in acetate buffer: 94.30 ± 5.03 mg/L for PM-150 and 107.99 ± 12.53 mg/L for PM-180, compared to Tris-HCl: 16.07 ± 0.66 mg/L for PM-150 and 8.86 ± 0.66 mg/L for PM-180, suggesting their potential for resorption by osteoclasts. Additionally, through MTT assays, the material was found to be non-cytotoxic (cell viability >70 %), showing no adverse effects on cell viability. In conclusion, the new fabrication method is promising to produce porous monetite. © 2025 Elsevier Ltd and Techna Group S.r.l. All rights are reserved, including those for text and data mining, AI training, and similar technologies.