This work addresses to joining aluminum alloy AA6061 to carbon steel AISI 1006 sheets using the friction spot joining technique. The steel sheets were pre-holed and threaded with an internal M6 thread. The joining process was carried out by extruding the aluminum through the steel hole and thread using a rotating tool with friction between the tool and aluminum. Three process parameters were used: pre-heating time, rotating speed and plunging depth of the tool, with four levels for each parameter. The results indicated that the two materials joined by a micro-scale mechanical interlock at an interface line of a width ranged between 0.7 to ~ 2.5 mm. The joint’s shear force reached a minimum and maximum value of 2000 and 2500 N, respectively. The plunging depth was the most effective factor affecting the amount of the extruded aluminum and the joint’s shear force.