In a regulatory statement, HL confirmed Mr Hargreaves had sold 19.5m shares in the business.
Both Mr Hargreaves and Mr Lansdown have been steadily reducing their stakes over the past few years.
The latest stake to be sold by Mr Hargreaves, in an institutional placing, is worth about one sixth of his 24% holding.
Following the sell off his stake in the business has been reduced to just under 20%.
Early last year he sold off a £500m stake in the firm he started with Mr Lansdown from a spare room.
In November Stephen Lansdown sold £103m of shares in the business, reducing his holding to 5.7%.
Mr Hargreaves, 74, continues to invest in a number of businesses. He has often been an outspoken figure in the investment world and was a prominent support and funder of the Brexit campaign.