In this study, the influence of pH adjustment sequence during green synthesis on the structural evolution of TiO2 nanoparticles was investigated, specifically examining whether the solution pH was modified before or after the addition of titanium(IV) isopropoxide (TTIP). Jatropha multifida leaf extract was employed as a natural reducing, capping, and stabilizing agent owing to its rich bioactive compounds, which are capable of directing nanoparticle formation. Two synthesis pathways were systematically compared: pre-pH adjustment, where the extract pH (∼5) was adjusted to acidic or basic conditions prior to TTIP addition, and post-pH adjustment, where TTIP was first introduced into the extract, followed by pH modification. The pH values were varied at 3, 7, and 10. The results revealed that the crystallite size increased with increasing pH, and for the same pH value, the post-pH adjustment route consistently produced larger crystallites than the pre-pH adjustment route. Following synthesis, all as-prepared samples were utilized as photoanodes in DSSCs, and their photovoltaic performance was evaluated via current–voltage (I–V) measurements under simulated solar illumination. The pre-pH 3 sample achieved the highest PCE of 5.52%, attributed to its smaller crystallite size, which provides a higher surface area, greater dye loading, and improved charge transport. Thus, the pre-pH adjustment method is more suitable for producing TiO2 for DSSC applications. This study demonstrates that the timing of pH adjustment controls TiO2 nucleation and growth, shaping its final structure, and affecting DSSC performance. It provides a simple, green, and scalable way to tune TiO2 for improved solar cell efficiency. © 2026 Faculty of Engineering, Universitas Indonesia. All rights reserved.