The regiment was formed on the creation of the Territorial Force in April 1908 and placed under orders of the Eastern Mounted Brigade. It was headquartered at Bury St Edmunds with the squadrons being headquartered as follows:
- A Squadron: Cambridge (with a drill station at Ely)
- B Squadron: Bury St Edmunds (Eye, Thetford, Sudbury and Stowmarket)
- C Squadron: Ipswich (Felixstowe, Framlingham and Woodbridge)
- D Squadron: Beccles (Bungay, Halesworth, Lowestoft and Leiston).
1/1st Suffolk Yeomanry
- August 1914 : moved with the brigade to Woodbridge and came under orders of 1st Mounted Division.
- July 1915: moved to Leiston.
- 25 September 1915 : dismounted and sailed from Liverpool on SS ‘Olympic’ for service at Gallipoli.
- 10 October 1915 : landed at Anzac cove and brigade under orders of 54th (East Anglian) Division.
- December 1915 : evacuated from Gallipoli and moved to Egypt.
- 22 February 1916 : Eastern and Southern Mounted Brigades formed 3rd Dismounted Brigade, on Suez Canal defences.
- July 1916 : brigade moves to join Western Frontier Force,
- 5 January 1917 : formally converted to infantry and became 15th (Suffolk Yeomanry) Battalion of the Suffolk Regiment. Placed under orders of 230th Brigade in 74th (Yeomanry) Division.
- 7 May 1918 : landed with division at Marseilles for service in France.
2/1st Suffolk Yeomanry
- Formed in September 1914 as a “second line” (training, draft-supplying reserve) for the 1/1st.
- Under orders of 2/1st Eastern Mounted Brigade from January 1915. Moved to Ely.
- March 1916: brigade became 13th Mounted Brigade, under orders of 4th Mounted Division at Wivenhoe.
- July 1916: converted to a cyclist unit in 5th Cyclist Brigade, under 2nd Cyclist Division.
- November 1916: merged with 2/1st Norfolk Yeomanry to form 7th (Suffolk and Norfolk) Yeomanry Cyclist Regiment, under command of 3rd Cyclist Brigade.
- March 1917 : resumed original identity but in same brigade, now in Ipswich area. Moved to Woodbridge by July 1917.
- May 1918: moved to Ireland, being at Boyle and Collooney.
3/1st Suffolk Yeomanry
- Formed as a “third line” (training, draft-supplying reserve for the 1/1st and 2/1st) in 1915.
- 1916: dismounted and attached to 3rd-Line groups of East Anglian Division at Halton Park (Tring).
- Early 1917: disbanded, some troops going to 2/1st Regiment and rest to 4th Reserve Battalion of the Suffolk Regiment.
In the 1917 renumbering of the Territorials, the Suffolk Yeomanry issued numbers from the block 305001-310000. Corps of Hussars.