Abstract Objective This study aimed to investigate the effect of hydroxyapatite from snakehead (Channa striata) fish bone on the surface hardness of the enamel of the primary teeth. Materials and Methods Twenty-six primary maxillary incisors were mounted on self-cured acrylic resin, divided into two groups, and demineralized. Remineralization was performed using hydroxyapatite paste synthesized from C. striata fish bone by the precipitation method. The case group was subjected to 15% hydroxyapatite paste and subsequently submerged in artificial saliva, while the control group was only exposed to artificial saliva. Enamel hardness was measured by the Vickers hardness tester after 7 days of treatment. The statistical analysis used in this research was an independent t-test. Results The case group had a surface hardness of 356.192 ± 25.218, and the control group had a surface hardness of 269.686 ± 22.931. Statistical tests showed a significant difference between the case and control groups. Conclusion Hydroxyapatite paste from snakehead (C. striata) fishbone stimulates remineralization of primary teeth, as evidenced by an increase in the enamel surface hardness of the teeth.