The 3rd New York Cavalry was organized by companies beginning in July 1861 and mustered in September 9, 1861 at Meridian Hill, Washington, D.C. under the command of Colonel James H. Van Alen.

The regiment was attached to Banks' Division, Army of the Potomac (5 companies), and Stone's Division, Army of the Potomac (6 companies), to December 1861.

Unattached, Department of North Carolina, to December 1862.

Unattached, XVIII Corps, Department of North Carolina, to May 1863.

1st Brigade, August Kautz's Cavalry Division, Army of the James, Department of Virginia and North Carolina, to December 1864.

Duty in the defenses of Washington, D.C., and on the Upper Potomac until April 1862.

Ordered to the Department of North Carolina April 6.

Swift Creek Bridge June 28 (detachment).

Reconnaissance to Young's Cross Roads July 26–29 (detachments).

Olive Station, Goshen Swamp, and Whitehall December 16.

Dudley Station, Thompson's Bridge, and Goldsborough December 17.

Reconnaissance to Pollocksville, Tranter's, Young's Cross Roads, and Onslow January 17–21.

Near Fairfield and Swann's Quarter March 3–4 (Company F).

Deep Gully New Bern, March 13–14 (detachment).

Near Dover, Core Creek, and Young's Cross Roads April 7.

Expedition to Swift Creek Village April 13–21 (detachment).

Raid on Wilmington & Weldon Railroad July 3–7 (detachment).

Tarboro and Rocky Mount Station July 20.

Swift Creek and Street's Ferry July 22.

Camden Court House and Dismal Swamp November 3.

Bettom's Bridge and Baltimore Cross Roads February 7.

Kautz's Raid on Richmond & Danville Railroad May 12–17.

Siege operations against Petersburg and Richmond June 16-December 1, 1864.

Wilson's Raid on South Side & Danville Railroad June 22–30.

Prince George Court House September 15.

Jerusalem Plank Road and Sycamore Church September 16.

Prince George Court House September 22.

Johnson's Farm and New Market Road October 7.

Operations about Broadwater Ferry, Chowan River, December 11–19.

Scout to South Quay January 2, 1865 (Companies A, B, C, H, and L).