The growth of in plane highly mismatched GaSb nanotemplates free of threading dislocations on GaAs (001) substrate is demonstrated using selective area growth. We report a detailed comparison of the crystalline quality of GaSb elaborated either as 2D layers or selectively grown inside 100 nm wide stripes directed along  or [1–10]. By means of transmission electron microscopy, we show that the GaSb layer grown on a bare substrate contains an important density of threading dislocations, while the one grown inside nano-openings is free from threading dislocations. Moreover, we demonstrate that the GaSb layers in both growth modes are relaxed through a Lomer dislocation network at the interface, which is characterized using the full width at half maximum of the GaSb X-ray diffraction peak for different reflections. Finally, we demonstrate that these GaSb nanotemplates can be used for subsequent epitaxial growth of high structural quality strained InAs nanowires.