The arrangement of nanoscale building blocks into patternswithmicroscale periodicity is challenging to achieve via self-assemblyprocesses. Here, we report on the phase-transition-driven collectiveassembly of gold nanoparticles in a thermotropic liquid crystal. Atemperature-induced transition from the isotropic to the nematic phaseunder anchoring-driven planar alignment leads to the assembly of individualnanometer-sized particles into arrays of micrometer-sized agglomerates,whose size and characteristic spacing can be tuned by varying thecooling rate. Phase field simulations coupling the conserved and nonconservedorder parameters exhibit a similar evolution of the morphology asthe experimental observations. This fully reversible process offerscontrol over structural order on the microscopic level and is an interestingmodel system for the programmable and reconfigurable patterning ofnanocomposites with access to micrometer-sized periodicities.