The Shrewsbury-born striker, who scored forty goals in eighty-six Saddlers appearances, was believed to be on the target list of several clubs over the summer but Barnsley were initially able to hold on to the former Aberystwyth Town man as the club seeks to return to the Championship at the first time of asking.
However, it is now understood that, with the striker keen to make the move, the clubs have come to terms on a £1,000,000 deal which will see the 26-year-old join Millwall on loan before the loan window closes at the end of the month.
Walsall, who sold Bradshaw to Oakwell-based Barnsley for an undisclosed fee in the summer of 2016, are believed to have a small sell-on clause in the forwards current deal and would stand to make a small amount of money from the profit which the Tykes will be making from the deal.
Tom is out of contract at the end of the season and is said to be keen to get back to playing football in the Championship. His representatives will now enter into contract negotiations with the London-based club with a deal looking likely to be completed over the coming days.