The use of carbon‐based nanomaterials as effective photocatalysts is an ideal alternative for environmental remediation. Here, (3‐aminopropyl)triethoxysilane‐functionalized carbon nanoparticles (SiCNPs) were prepared using a simple pyrolysis method with sodium citrate and urea as the precursors. The samples were characterized by X‐ray diffraction, transmission electron microscopy, ultraviolet–visible diffuse reflectance spectroscopy, X‐ray photoelectron spectroscopy, photoluminescence spectroscopy, and photo‐electrochemical measures. The obtained SiCNPs‐2.0 showed a better visible light response and more effective photocatalytic activity for degradation of methylene blue (MB) compared with pure CNPs. Under visible light irradiation, 98.8% of the MB was decomposed within 75 min when SiCNPs‐2.0 was used as the photocatalyst. The high photocatalytic activities of SiCNPs‐2.0 could be attributed to enhanced light absorption in the visible region, and improved photogenerated electron–hole separation efficiency. A possible photocatalytic mechanism for removal of MB over SiCNPs‐2.0 was proposed based on active species trapping experiments. Recycling experiments showed that SiCNPs‐2.0 had good stability during photocatalysis. This work provides a new easy method to synthesize carbon‐based nanomaterials and to catalytically degrade organic pollutants in water under visible light irradiation.