Molecular self-assembly is an efficient approach to fabricate supramolecular nanostructures on well-defined surfaces. The nanostructures can be regulated through functionalizing the molecular precursors with different functional groups. Here, from an interplay of high-resolution scanning tunneling microscopy imaging and density functional theory calculations, we have at the atomic scale investigated the influence of tert-butyl groups on the on-surface self-assembled behaviors of the organic molecules where intermolecular interactions mainly originate from relatively weak van der Waals interactions. Our results demonstrate that the tert-butyl groups can not only affect the adsorption geometry but also change the self-assembled properties of organic molecules on surfaces due to the enhanced intermolecular interactions.