This study aims at the synthesis of gold nanoparticles (2–3 nm) functionalized with different nitroalkane-terminated thiols and investigates the chemical reactivity of these confined nitroalkanes towards aldehydes to yield β-nitroalcohols. Interfacial Henry reaction between fixed nitroalkane-terminated thiols with various aromatic and heteroaromatic aldehydes resulted in stereogenic centers on the surface of mixed-monolayer-protected gold nanoparticles (MMPNs). The ratio of the resulting diastereomers was determined by 1H NMR spectroscopy. It was found that some parameters such as the chain length of nitroalkyl and the nature of aromatic aldehyde play the main role in affecting the diastereomeric ratio on the surface of MMPNs. Certain trends have been analyzed from the data, and it can be inferred that some aldehydes approximately prefer the formation of anti diastereomers as the predominant products, while others give syn β-nitroalcohols. We have attributed this stereoselectivity to the packed layers, forceful lateral interactions (van derWaals), and intramolecular hydrogen bonding on the surface of modified gold nanoparticles that are able to suppress the role of solvent and intermolecular interactions.