SeaMARC II side‐scan imagery and bathymetry, seismic reflection, and free‐fall core sampling data reveal the morphology, structure, and hydrology controls on the formation and development of a series of crescent‐shaped slab slides along the submarine canyon walls in the Arequipa fore‐arc basin off southern Peru. The crescent‐shaped slab slides occur in a segment of an approximately 25‐km‐long canyon course and generally accord with the meandering of the canyon course. Most of the slab slides commonly consist of four distinctive zones: the fissured zone, scarp zone, voided zone, and frontal zone. The fissured zone is developed on the crown of the sliding walls; the scarp zone is marked by scars with crescent‐shaped slip surfaces and throws ranging from 50 to 120 m. The voided zone is characterized by 1–3 km wide terraces resulting from slab‐type excavating of the seafloor. The frontal zone is normally comprised of debris materials distributed on the seafloor near the canyon thalweg; however, there is lack of debris materials in some frontal zones, probably due to canyon erosion. The formation and development of the slab slides are probably attributed to five major factors: the homoclinal setting, faults and lithology of the strata, extensive weak strata contacts, interstrata‐fluid movement that can be compared to groundwater sapping processes on land, and earthquakes. The homoclinal setting in the uppermost section of the fore‐arc basin prepared a favorable condition for the canyon wall failure by providing a lateral continuity of a potential failure plane. The faults and lithology of the strata control the lateral margins of the slides. The extensive weak strata contacts within the homoclinal section provided a substantial failure surface for the slab slide. The interstrata‐fluid movements may lead to (a) the degradation of the strata strength through undermining of the strata contacts resulting from a lowering of friction, and (b) the collapse of canyon walls by removal of basal support or oversteepening as a result of enhanced erosion by the sapping process of the interstrata fluid. The formation of the crescent‐shaped slab slides was probably further facilitated by the triggering effect of earthquakes associated with the subduction of the Nazca plate under the Peru margin.