One of the three sons of Zeruiah, David's sister, and “captain of the host” during the whole of David's reign (2 Sam. 2:13; 10:7; 11:1; 1 Kings 11:15)
His father's name is nowhere mentioned, although his sepulchre at Bethlehem is mentioned (2 Sam. 2:32). His two brothers were Abishai and Asahel, the swift of foot, who was killed by Abner (2 Sam. 2:13-32), whom Joab afterwards treacherously murdered (3:22-27). He afterwards led the assault at the storming of the fortress on Mount Zion, and for this service was raised to the rank of “prince of the king's army” (2 Sam. 5:6-10; 1 Chr. 27:34).
His chief military achievements were, (1) against the allied forces of Syria and Ammon; (2) against Edom (1 Kings 11:15-16); and (3) against the Ammonites (2 Sam. 10:7-19; 11:1, 11).
His character is deeply stained by the part he willingly took in the murder of Uriah (11:14-25).
He acted apparently from a sense of duty in putting Absalom to death (18:1-14).
David was unmindful of the many services Joab had rendered to him, and afterwards gave the command of the army to Amasa, Joab's cousin (2 Sam. 20:1-13; 19:13). When David was dying, Joab espoused the cause of Adonijah in preference to that of Solomon. He was afterwards slain by Benaiah, by the command of Solomon, in accordance with his father's injunction (2 Sam. 3:29; 20:5-13), at the altar to which he had fled for refuge. Thus this hoary conspirator died without one to lift up a voice in his favor.
He was buried in his own property in the “wilderness,” probably in the northeast of Jerusalem (1 Kings 2:5, 28-34). Benaiah succeeded him as commander-in-chief of the army.