The agency won the account from Birmingham-based Rewired PR in a four-way pitch.
On the back of the win, Golley Slater's London office has won the media buying account for Poundstretcher.
As well as raising the profile of the business, Leeds-based Golley Slater North will be charged with creating campaigns alongside the internal marketing team at Poundstretcher.
York, who became MD last August, oversaw the agency selection process. Under his leadership, the company plans to grow from just over 400 to 500 sites within 18 months.
He said: "This is a very exciting time for our growing business and so we needed to switch our communication support to a strong agency with proven national credentials."
The team at Golley Slater North impressed us with its proven retail background, balanced with a superior and creative approach to our brief."
Eileen Stretton, MD of Golley Slater North, added: "It’s another brand that fits well with our business model as, in addition to the national capability of our locally based team, the client has the unique opportunity to use the Golley Slater regional network, meaning marketing experts can be close to their stores wherever they are across the UK."
Poundstretcher recently reported strong trading performance over the festive period, with 14.8 per cent total sales growth and a 10.4 per cent rise in like-for-like sales in the five weeks to 30 December.
In the past six months Golley Slater's northern branch has won accounts for property group Land Securities (Trinity Leeds & White Rose), Thai Leisure Group and projects for GO Outdoors.