Pompey will host fellow Championship side Millwall in the first round of the Carabao Cup.
The tie is set to be played at Fratton Park in the week commencing August 12.
It will be just the second time that the two sides have met in this competition, although the previous occasion was as recently as 2021.
That took place at The Den, with the Lions fighting from behind to win 2-1 after Reeco Hackett had opened the scoring.
Millwall were beaten 4-0 at home to Reading at this stage of the Carabao Cup last season, while the Blues saw off Forest Green before losing to Peterborough on penalties in round two.
A confirmed date for the tie and ticket details will be announced in due course.