The defender's solitary goal separated the two teams in a match more reminiscent of a pre-season friendly than the Championship.
The result was Stoke's first win of the season and sent Millwall crashing to the bottom of the league.
Hall punished the Lions for failing to clear their lines after Luke Chadwick had played the ball into Bruce Dyer's feet.
The former Crystal Palace striker was hastily dispossessed by Mark Phillips only for the ball to fall kindly for Hall, who blasted in a right-footed drive that Andy Marshall had little chance of saving.
Both sides had chances to take the lead before then, with Millwall's coming in the 40th second after Josh Simpson had fed Barry Hayles. But the striker was unable to connect with pass and his shot skidded wide of the post.
A minute later Stoke had the ball in the net when Dyer finished off a neat free-kick, but the striker saw his effort ruled out after he moved into an offside position.
Michael Duberry and Chadwick also went close while Millwall could have drawn level in the dying minutes when Phillips' header was stopped on the line.