In recent years, there has been an increase in demand for inexpensive biowaste-derived photocatalysts for the degradation of hazardous dyes and pharmacological drugs. Here, we developed eggshell derived hydroxyapatite nanoparticles entrenched on two-dimensional g-C₃N₄ nanosheets. The structural, morphological and photophysical behavior of the materials is confirmed through various analytical techniques. The photocatalytic performance of the highly efficient HAp/gC₃N₄ photocatalyst is evaluated against methylene blue (MB) and doxycycline drug contaminates under UV–visible light exposure. The HAp/gC₃N₄ photocatalyst exhibit excellent photocatalytic performance for MB dye (93.69%) and doxycycline drug (83.08%) compared to bare HAp and g-C₃N₄ nanosheets. The ultimate point to note is that the HAp/gC₃N₄ photocatalyst was recycled in four consecutive cycles without any degradation performance. Superoxide radicals play an important role in degradation performance, which has been confirmed by scavenger experiments. Therefore, the biowaste-derived HAp combined with gC₃N₄ nanosheets is a promising photocatalyst for the degradation of hazardous dyes and pharmacological drug wastes.