Abstract: The present study focused on developing a modified form of C.I. Pigment Red (PR) 170 with the aim of enhancing its performance characteristics while lowering manufacturing costs. Silica fume was incorporated as a modifying agent during the pigment synthesis process. Under acidic conditions, silica fume was introduced into a diazonium salt solution and activated to create reactive surface sites. A coupling component was then slowly added, enabling the pigment to form directly and uniformly on the silica fume surface through an in-situ modification approach. The structural and functional properties of the modified pigment were investigated using several analytical techniques, including Fourier Transform Infrared Spectroscopy (FT-IR), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Thermogravimetric Analysis (TG-DTA), UV–Visible Diffuse Reflectance Spectroscopy (UV-Vis DRS), and CIE Lab* color measurements. Experimental results demonstrated that silica fume significantly influenced pigment morphology and particle size, leading to the formation of a distinct core–shell structure. The modified pigment exhibited superior colour strength, enhanced thermal stability, improved migration resistance, better water dispersibility, and greater resistance to ultraviolet radiation compared with the conventional pigment. Further studies are required to examine the relationship between silica fume concentration, pigment layer thickness, and the resulting performance characteristics. The proposed modification technique offers an effective strategy for improving PR170 properties while utilizing industrial waste materials, thereby reducing production expenses and supporting sustainable resource management. In addition, the method is versatile and may be applicable to the modification of other organic pigments. The integration of pigment synthesis and modification into a single process represents a novel aspect of this work and contributes to the development of pigments with improved suitability for ink and coating applications.