We report the first structural field mapping of exhumed mud volcano feeder complexes. Three mud volcanoes outcropping onshore in Azerbaijan were selected on the basis of outcrop quality and scale. These examples are all located within 1 km of the axes of NW-SE-trending folds associated with the southern margin of the Greater Caucasus mountain belt. The mapping shows that the intrusive complexes are 200-800 m wide and roughly circular. These feeder complexes consist of a megabreccia of country rock blocks at a scale of tens of metres, enclosed in a matrix of intrusive mud. Minor structures include grid like fractures sets, sinuous fractures, mud plugs and breccia pipes. The country rock blocks are deformed and rotated relative to surrounding sedimentary strata. Alternative mechanisms to explain the strain history of these large blocks in the feeder complexes are: a. stoping, b. flow rotation and c. caldera collapse. Our mapping indicates that the most likely mechanism involves stoping processes, similar to those identified in igneous systems. This study provides a basis for reservoir distribution in commercial geological models that contain the feeder complexes of mud volcano systems, and also constrains conduit geometry for modelling studies of evolution and flow dynamics. © 2009 The Authors. Journal Compilation © Blackwell Publishing Ltd, European Association of Geoscientists & Engineers and International Association of Sedimentologists.