The regiment was attached to Runyon's New Jersey Brigade, Defenses of Washington, to June 1861. 1st Brigade, Runyon's Reserve Division, McDowell's Army of Northeast Virginia, to July 1861.
Left New Jersey for Annapolis, Maryland, May 3. Reported to General Butler May 5, then moved to Washington, D.C., arriving there May 6. At Meridian Hill until May 24. Occupation of Arlington Heights, Va., May 24. Construction of Fort Runyon. Duty on line of Alexandria & Loudon Railroad until July 16. Advance on Manassas, Va., July 16-21. Battle of Bull Run July 21 (reserve).
The 4th New Jersey Infantry mustered out of service July 31, 1861.