Surface geology, well data and 2D seismic interpretations reveal the presence of triangle zone structures at the contact of the Subandean Ranges and the Amazonian foreland in Peru. From north to south the Santiago, Marañon, Ucayali and Madre de Dios basins have been studied. Interpretations presented in this study show a great variety of structural styles at this contact area. Simple triangle zones with one back thrust, composite ones with several back thrusts, more complex double vergent ones with pop-up structures, best described as fish-tails, tectonic wedges and passive-roof duplexes are present in the study area. The role of pre-Andean tectonics and paleogeography is key to understanding the Andean evolution, due to the control on the location and geometry of the main detachment levels. The Santiago Basin is characterized by the presence of fish-tail structures with a Permian-Triassic evaporitic basal detachment located at the base of the Pucara Gr. At the Ucayali Basin, several detachment levels interact, the basal ones located within the Ordovician, Devonian, and Carboniferous defining triangle zones or tectonic wedges. At the Madre de Dios Basin, two detachment levels define the base of the triangle zone, Permian shales in the northwest at the Inambari Imbricates area, and Lower Devonian (Cabanillas Gr.) in the southeast at the Candamo area. A roof thrust is located within the Paleogene section at both the Madre de Dios and Ucayali basins, defining passive-roof duplex structures. Several detachment levels are rooted into the Lower Paleozoic; others within the Permian-Triassic section, being locally evaporitic, and finally others are located at the base of the Cretaceous. Paleozoic shales represent the main basal detachment level of the southern Subandean ranges. The role of these detachments and the role of the sedimentation rate are discussed as factors that control the development and geometry of the triangle zones described in the study area. Except for the San Martin-Sagari area of the Ucayali Basin, the triangle zones of the Santiago and Madre de Dios basins remain unexplored even though active petroleum systems are present. Sub-thrust structures at the Azulmayo area of the Madre de Dios Basin remain promising undrilled structures. •From north to south, the structure of the Subandean Ranges of the Peruvian Andes, that is the Santiago, Marañon, Ucayali and Madre de Dios Basins has been described using surface geological maps and cross-sections, well logs and 2D seismic data.•Triangle zones develop at the contact between the east-vergent Paleozoic-Mesozoic imbricates/duplex of the Andes foothills with the Amazonian foreland basin.•The main detachment varies from Lower Paleozoic, Permian and Cretaceous shale strata, being Permian-Triassic evaporites at the Santiago Basin. Tectonic activity developed from Cretaceous to Quaternary time.•The structural style is very variable from basin to basin and consists of simple (one back thrust) to composite triangle zones (with associated pop-up structures or multiple back thrusts), best described as fish-tails, tectonic wedges or passive-roof duplexes.•The role of detachment levels and sediment loading and rate, specially of syn-orogenic growth strata, will be discussed to explain the development of triangle zones in the study area.