Formaldehyde is considered as a common pollutant in industrial wastewaters requiring removal techniques designed to reduce its harmful effects due to distribution in the environment. In this study, TiO2 nanoparticles are modified through nitrogen doping by sol-gel technique and their photo-catalytic performance for formaldehyde degradation is studied under UV and solar irradiation. Various characterization techniques such as: PSA, FTIR, XRD, and SEM are performed on the synthesized nano-photocatalyst with a similar to 20 nm average size. The significance of parameters such as initial formaldehyde concentration, catalyst molar ratio N/Ti, pH, and removal time under UV and solar radiation are assessed using response surface methodology based on central composite design. Formaldehyde removal was measured as a function of irradiation time using UV-Visible spectrophotometry. The results show that the maximum formaldehyde removal at optimal conditions (pH = 5 for 400 ppm initial formaldehyde concentration) by nitrogen-doped TiO2 is 64.02 % under solar and 60.15 % under UV radiation suggesting it as an effective photo-catalyst for formaldehyde removal.