This study reports the successful synthesis of Zinc(Zn):Iron (Fe) codoped titanium dioxide (TiO2) nanoparticles (Z:F-T NPs) using the sol–gel method. Various codoping ratios are employed, with a 5 mol% dopant concentration added to a constant amount of tetraisopropyl orthotitanate, ethanol, and diethanolamine. This is done to improve the light absorption efficiency of the photoanode TiO2, which helps to reduce electron-hole recombination, improve charge carrier abilities, and enhance its electrical properties. The resulting brown gel is annealed in a muffle furnace at 500 °C for the anatase phase and 800 °C for the rutile phase. The effects of Zn:Fe codoping are observed in the Fourier transform infrared analysis with the suppression of characteristic IR vibration. X-ray diffraction (XRD) analysis confirms the presence of anatase and rutile phases. In the anatase phase, codoping leads to the appearance of new diffraction peaks and the suppression of others, attributed to Fe occupying interstitial positions and Zn substituting Ti4þ. The largest crystallite size of 24.45 nm is observed for the 1:0.5 Z:F-T NPs. Conversely, the same codoping ratio in the rutile phase shows a reduced crystallite size of 18.28 nm, highlighting the phase-dependent behavior of structural growth. Ultraviolet–visible spectroscopy shows a slight increase in the estimated bandgap for both phases. Scanning electron microscopy analysis collaborates with the XRD findings by revealing dense and smooth NP surfaces in the anatase phase, while the rutile phase exhibits minimal morphological changes. Energy-dispersive X-ray confirms the presence of Zn, O, and Ti in the anatase phase and Zn, Fe, Ti, and O in the rutile phase, supporting successful dopant incorporation. The study concludes that high Zn concentration codoped with Fe to TiO2 anatase phase induces lattice distortion that improves its structural and optical properties, while the stability of the rutile phase resists structural modifications.