Here, we present an innovative and creative sustainable technique for the fabrication of titania (TiO₂) using Acorus calamus (A. calamus) leaf extract as a new biogenic source, as well as a capping and reducing agent. The optical, structural, morphological, surface, and thermal characteristics of biosynthesized nanoparticles were investigated using UV, FTIR, SEM, DLS, BET, and TGA-DSC analysis. The phase formation and presence of nanocrystalline TiO₂ were revealed by the XRD pattern. FTIR analysis revealed conjugation, as well as the presence of Ti–O and O–H vibrational bands. The nanoparticles were noticed to be globular, with an average size of 15–40 nm, according to the morphological analysis, and the impact of size quantification was also investigated using DLS. The photocatalytic activity of bare, commercial P-25 and biosynthesized TiO₂ (G-TiO₂) nanoparticles in aqueous solution of rhodamine B (RhB) dye was investigated under visible light irradiation at different time intervals. The biosynthesized TiO₂ nanoparticles exhibited strong photocatalytic activity, degrading 96.59% of the RhB dye. Different kinetic representations were utilized to analyze equilibrium details. The pseudo-first-order reaction was best suited with equilibrium rate constant (K₁) and regression coefficients (R²) values 3.72 × 10⁻⁴ and 0.99, respectively. The antimicrobial efficacy of the prepared nanoparticles was investigated using the disc diffusion technique. Further, biosynthesized TiO₂ showed excellent antimicrobial activity against the selected gram-positive staining (B. subtilis, S. aureus) over gram-negative (P. aeruginosa, E. coli) pathogenic bacteria in comparison to bare TiO₂.