Pollution due to pharmaceutical contaminants has emerged as a significant ecological issue, affecting water quality, marine ecosystems, and humans across the globe. Due to the increasing concern over pharmaceutical pollutants, effective and sustainable treatment methods are of critical need. This study investigates the solar-assisted photocatalytic degradation of tetracycline hydrochloride (TCT), a persistent pharmaceutical contaminant in aqueous systems, using magnetite nanoparticles as immobilized catalyst. The catalyst was synthesized using a precipitation method. Key operational variables influencing degradation efficiency were systematically analyzed. The degradation followed pseudo-first-order kinetics with approximately 48% TCT removal within 30 minutes and up to 99% within 120 minutes under sunlight exposure. The introduction of a Fenton reagent notably enhanced the photocatalytic performance. The synthesized catalyst was characterized using various techniques. The process also contributed to a reduction in chemical oxygen demand (COD), and by using liquid chromatography–mass spectrometry (LC-MS), the intermediates during the degradation were identified. The catalyst reusability tests indicated minimal loss in activity over successive cycles. These findings highlight the viability of integrating solar energy with immobilized magnetite nanocatalysts for sustainable wastewater treatment, offering an effective method for removing antibiotic residues and promoting water reuse. Future research should focus on exploring new magnetite composites and the potential for integrating this technology with real-world applications.