Outcrop data from SE Crete and a high‐quality seismic volume from SE Brazil are used to characterize five types of mass‐transport deposits that are clear markers of tectonism in extensional basins. They include (1) carbonate blocks and breccia‐conglomerates showing limited gravitational collapse; (2) disrupted blocks, carbonate megabreccias, and boulder conglomerates on tectonically active slopes; (3) blocks and debris‐flow deposits accumulated distally from exposed fault scarps; (4) chaotic volumes of turbidites, chalk, and evaporites; and (5) continental/shallow‐marine debris cones derived from fault scarps. At outcrop, submarine slide blocks are observed on the slopes of tectonically active basin shoulder highs. The slide blocks occur together with sandy mass‐transport deposits that reflect the remobilization of “background” slope sediment (types 3 and 4). Soft‐sediment deformation styles document important shearing within blocks and their basal shear zones. On 3D seismic data, early‐stage mass‐transport deposits reveal important faulting and the generation of a thick basal shear zone. Mass‐transport deposits of types 1 and 2 alternate in space with type 4 intervals. We propose that the classification of mass‐transport deposits in this work can be used to recognize syn‐rift units accumulated in extensional settings throughout the world, particularly when tectonic subsidence outpaces sedimentation to hinder the deposition of “typical” syn‐rift growth geometries.