We propose a scaling law that explicitly correlates the macroscopic yield stress of weakly attractive nanoparticle networks with features of the microscopic aggregates that form the percolating gel. The proposed law correctly predicts experimental data obtained from a model colloidal system covering a wide range of particle sizes, volume fractions and interparticle attractive forces. The agreement between theory and experiments supports the idea that yielding is ultimately caused by the rupture of a few interparticle bonds within the aggregates of the mechanically loaded network. © 2011 The Royal Society of Chemistry.