Vietnam War Medal of Honor Recipient. He received the award posthumously (presented to his wife) from Vice President Spiro T. Agnew at the White House on December 2, 1969, for his actions as a Staff Sergeant with Company D, 2nd Battalion (Airborne), 501st Parachute Infantry Regiment, 101st Airborne Division, U.S. Army, on February 21, 1968, during the Battle of Hue, South Vietnam. Orphaned as a young child, he was adopted at the age of 13.

After graduating from high school, he joined the U.S. Army and, after his airborne training, he was sent to South Vietnam. On that day, during an engagement with enemy forces near Huế in the Republic of Vietnam, he threw himself onto a triggered booby trap and was killed in the ensuing explosion, He was also awarded the Purple Heart.

His Medal of Honor citation reads: "For conspicuous gallantry and intrepidity in action at the risk of his life above and beyond the call of duty. S/Sgt. Sims distinguished himself while serving as a squad leader with Company D. Company D was assaulting a heavily-fortified enemy position concealed within a dense wooded area when it encountered strong enemy defensive fire. Once within the woodline, S/Sgt. Sims led his squad in a furious attack against an enemy force which had pinned down the 1st Platoon and threatened to overrun it. His skillful leadership provided the platoon with freedom of movement and enabled it to regain the initiative. S/Sgt. Sims was then ordered to move his squad to a position where he could provide covering fire for the company command group and to link up with the 3rd Platoon, which was under heavy enemy pressure. After moving no more than 30 meters S/Sgt. Sims noticed that a brick structure in which ammunition was stocked was on fire. Realizing the danger, S/Sgt. Sims took immediate action to move his squad from this position. Though in the process of leaving the area, 2 members of his squad were injured by the subsequent explosion of the ammunition, S/Sgt. Sims' prompt actions undoubtedly prevented more serious casualties from occurring. While continuing through the dense woods amidst heavy enemy fire, S/Sgt. Sims and his squad were approaching a bunker when they heard the unmistakable noise of a concealed booby trap being triggered immediately to their front. S/Sgt. Sims warned his comrades of the danger and unhesitatingly hurled himself upon the device as it exploded, taking the full impact of the blast. In so protecting his fellow soldiers, he willingly sacrificed his life. S/Sgt. Sims' extraordinary heroism at the cost of his life is in keeping with the highest traditions of the military service and reflects great credit upon himself and the U.S. Army."