We report on a universal technique which allows us to precisely manipulate the diameter of metal nanoparticles in two-dimensional particle arrays. The approach is demonstrated here for hexagonally ordered gold nanoparticle arrays fabricated by means of diblock copolymer micelle lithography(BCML). The particles are used as nucleation centers in seed-mediated photochemical metal deposition, whereby the particle diameter increases. Repeatedly combining photochemical growth with thermal annealing steps additionally facilitates controlling the shape of the particles.