Assembly Member for Montgomeryshire, Russell George, is urging residents to take part on December 7.
Mr George said: "Small Business Saturday is a wonderful opportunity to champion the key role played by small firms across Powys's high streets.
"But, as the retail market changes, I am encouraging people across Montgomeryshire to join me on December 7 in pledging to shop locally to support the independent businesses we all know and love."
He added: "The changing retail market has been challenging for businesses to adapt as more people head to out-of-town shopping centre and online.
"During the lead-up to the campaign, I've been able to meet and chat to independent shop owners in Welshpool, Newtown, Llanfyllin, Machynlleth and Llanidloes.
“Our local high streets are instrumental in bringing people together – acting as a meeting place for friends and families and supporting jobs for local people. Let's do all we can to ensure that our high streets can flourish."