This has seen the Blues boss claim all three points in 29 of his 66 outings in the dugout for the south coast side.
The former Lincoln man arrived at PO4 in March 2021 - winning seven of his first 12 games in charge, albeit missing out on play-off football in the 2020-21 campaign.
Last term, he guided Pompey to a 10th place finish in the table, guaranteeing the Blues an unwelcomed sixth season in League One.
But how does Cowley’s win percentage since his arrival at Fratton Park compare to every other boss in the third tier?
We’ve taken a look at each manager’s win rate since taking over to see who has the highest average in League One.
Here’s what we found.