Seaway Mall opened on April 23, 1975 with over 60 retail stores plus a twin movie theater. Early anchor stores included Woolco, Kmart, and Miracle Food Mart. An expansion in the late 1980’s added a Sears store, which opened in 1989. In the late 1990’s the movie theatre expanded to include 7 screens, and both of the mall's resident discount department stores changed their names: Woolco was converted into a Walmart, and Kmart was converted into a Zellers.
In October 2012, a large Sport Chek opened up in the mall near Sears, and Target opened its doors in the summer of 2013. With the opening of Target, Seaway Mall became one of the few Canadian malls to have ever featured three very large discount department stores from the United States: Walmart, Target and Kmart, operating in the same mall at different points in time.
In January 2015, Target announced it had filed for bankruptcy, and would discontinue all Canadian operations. Target closed its doors on April 1, 2015, followed by the closure of the mall's Sears on September 30, 2015.
The former Sears is now split in half; a large Staples outlet occupies one half, while the other half is operated by the Canadian discount store Hart. In 2017 casual dining restaurant chain Mr. Mikes opened its first location in Ontario on the Seaway Mall grounds. The Welland Public Library moved into Seaway Mall with a full-service public library branch which opened on June 27, 2017. Current large format anchor stores includes tenants such as Sport Chek, Cineplex Entertainment, Winners and Shoppers Drug Mart.