The photocatalytic activity of BaBi4Ti4O15 with excess bismuth oxide (0–10 wt%) and the parametric study of photocatalysis are investigated in this article. BaBi4Ti4O15 with excess bismuth oxide was synthesized via a solid-state route followed by calcination at 950 °C for 4 h. All BaBi4Ti4O15 samples were characterized by X-ray diffractometer, scanning electron microscopy, energy dispersive X-ray spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and direct optical bandgap. Synthesized BaBi4Ti4O15 with excess bismuth oxide has an orthorhombic perovskite crystal structure with A21am space group. Excess bismuth varies in the concentration of oxygen vacancies, and 8 wt% excess BaBi4Ti4O15 has maximum oxygen vacancy. Excess bismuth also changes direct bandgap; the lowest bandgap is 2.33 eV for 8 wt% excess bismuth. The photocatalytic activity of BaBi4Ti4O15 with excess bismuth oxide (0–10 wt%) showed that 8 wt% excess bismuth has the highest photocatalytic activity. The parametric study of photocatalysis used the initial concentration, volume, and light source intensity as variables. The parametric study suggested that initial concentration, intensity, and volume were correlated with the degradation rate. Indoor dye cleaning in normal room light was also tested for real-life demonstration. BaBi4Ti4O15 was also characterized by an X-ray diffractometer and X-ray photoelectron spectroscopy to investigate the effect of photocatalysis.