The uniaxial compression of a monolayer of nanosized monodisperse spherical particles adsorbed at a planar interface is simulated using the Brownian dynamics technique. Initially, the particles spread at the interface form crystalline loosely interconnected clusters. As the interface is compressed, the gaps between the clusters are removed and a close-packed monolayer is formed. At this stage, the structure of the interface consists of two-dimensional crystalline grains separated by defect boundaries. Further interfacial compression induces desorption of nanoparticles at these boundaries and creates striplike patterns of a secondary adsorbed layer. The structural features observed show remarkable agreement with recent experimental studies of the compression of gold nanoparticles in a Langmuir trough.