The gallery, which holds nearly 1,000 works in its permanent collection, is named after Sir Alfred East, the landscape painter born in Kettering.
He was knighted in 1910 and served as president of the Royal Society of British Artists before his death in 1913.
Work to repair the Grade II listed building has cost £4.8m, although it was initially given a budget of up to £6.8m.
“My job [after the gallery opens] is to welcome people back in and then to work on the future programme of events,” Stevenson added.