It means that Adderley, the son of the homeware retailer’s founders Bill and Jean Adderley, is cashing in £192mln.
Following the placing, the aggregate holdings of the Adderley family are 43.2%, with Will Adderley retaining a 17.8% stake.
The FTSE 250 group said Adderley remains “fully committed” to his role as deputy chairman and has agreed not to sell further shares for another 90 days.
In another update published late on Monday, Dunelm said Adderley was looking to diversify his portfolio and the last time he sold shares was April 2016.
Shares dropped 10% to 1,272.04p on Tuesday at the opening bell.