Lenglet is set to join Atletico on a loan deal for the upcoming season.
The defender has been available from Barca since the end of last season after spending the campaign on-loan with Aston Villa.
Lenglet will join in a straight loan as Atletico do not have room to spend big on another permanent deal. Atletico have so far spent €190m this summer market.
Atletico will pay a percentage of Lenglet's salary for the season to close the arrangement.