Recent research has focused on the crystal growth of strontium phosphates via different methods due to the bioactivity and biocompatibility of these materials with bone tissue. Here, we use a biomimetic method to synthesize strontium hydrogen phosphate/gelatin composites via single diffusion in gelatin. We compare the composite crystals with analytical-grade strontium hydrogen phosphate using infrared spectroscopy (IR), scanning electron microscopy (SEM), thermal gravimetric analysis, and X-ray diffraction. The IR spectra reveal that gelatin is incorporated into strontium hydrogen phosphate crystals due to CH₂ and amide I vibrations. The SEM data exhibit arrow-like crystals and microspheres of strontium hydrogen phosphate with bundled nano-flakes and flower-like surface arrangements of crystals. Furthermore, we find that the thermal stability of the strontium hydrogen phosphate/gelatin composite crystals is higher than that of the analytical-grade strontium hydrogen phosphate. The ion concentration and the preparation method had only a small influence on the broadening of the X-ray Bragg reflections. Our study confirms that gelatin is a useful hydrogel for studying the crystallization of strontium hydrogen phosphate.