This work explores the promotion effects of employing our proposed mechanical ultrasonic-activated precipitation (MUP) technique on the different features (textural, morphological, thermal, optical, and photo/catalytic) during the synthesis of hematite nanoparticles compared to the conventional chemical precipitation pathway (CPP). X-ray diffraction data revealed the higher amorphicity, microstrains, and lattice defects for the pristine MUP products over CPP. Also, it confirmed the inverse interdependence between the lattice microstrains and the crystallite size. Microstructural and morphological analyses showed a decrease in the average particles' sizes by a factor of 20%, 28% and 39% upon applying MUP at precursor concentrations of 0.05M, 0.15M, and 0.45M, respectively. Moreover, it exhibited higher values of surface area with roughness, mesoporosity and better uniformity over CPP products. A detailed thermal study figured the interdependence correlation between the particle's crystallinity, employed pathway, and the precursor concentration, showing higher crystallinity for CPP within a shorter temperature range over the poorly crystallized MUP products. Besides, it depicted that the proper calcination temperature is <500 °C upon using ferric sulfate precursor compared to literature. The optical findings portrayed, upon decreasing the particle size as well as applying the MUP, a considerable blue shift in the bandgap energy in addition to an obvious decrease in the photoluminescence band intensity, suggesting enhancement in the photocatalytic performances compared to CPP. MUP displayed superior photocatalysts for the hydroxylation reaction of terephthalic acid, showing a linear correlation between the fluorescence intensity and the illumination time and obeying zero-order reaction kinetics. MUP also revealed competent catalysts for the degradation of toxic Congo Red (in dark) and reduction of hazardous 4-nitrophenol, following pseudo-first-order reaction kinetics. Additionally, it depicted two times higher stability and resistance to the catalyst poisoning over CPP products. Accordingly, this study could establish a striking piece of evidence for adopting MUP technique as a novel approach not only for the synthesis of hematite or other nanomaterials but also as a greener replacement to the conventional CPP.