In the present investigation, plates from 7020-O Al plates were joined using friction stir welding (FSW). The effect of FSW parameters on the microstructural and mechanical characteristics of the friction stir (FS) welded joints were evaluated. Three tools having different pin profiles, typically, tapered cylindrical pin (TCP), two flat sided cylindrical pin (TFSCP), and triangular pin (TRP) were used to weld the AA7020-O Al plates. The FSW was conducted at two different tool rotational speeds of 1400 and 1800 and at two different welding speeds of 20 and 40 mm/min. The results revealed that the dynamically recrystallized zone (DRZ) of the AA7020-O Al plates joined using the TRP tool exhibited the minimum size of primary α-Al grains. For all pin profiles, the average size of α-Al grains, at the central portions of DRZs, decreases significantly with increasing the welding speed; however, it is slightly decreased with increasing the tool rotational speed. The plates FS welded using TRP and TCP exhibited the highest and lowest values of the average hardness at the DRZs, respectively.