Investigations at the site of Huacas de Moche—also referred to as Huacas del Sol and de la Luna—on the north coast of Peru show a continuous occupational sequence from around AD 100 to 1500. The longest occupation corresponds to the Moche culture from around AD 100 to 850. Based on available archaeological evidence, this article examines the impact of an El Niño-like event in AD 600 on the history of Huacas de Moche. Widely held hypotheses assumed that this kind of climatic event caused the abandonment of the site; however, such explanations do not fit the current data. After almost three decades of research, archaeological evidence indicates that after the El Niño-like phenomenon of AD 600, the Old Temple of Huaca de la Luna was closed down, and the New Temple was built toward the east of the previous one, on the same slope of Cerro Blanco. Furthermore, on the opposite side of the site, the building called Huaca del Sol experienced its last and greatest architectural expansion, becoming a large-scale palace. These new lines of evidence lead us to reassess the effect that the El Niño-like phenomenon of AD 600 had on the development of the Moche culture at the site.