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.
1. John Coleman - Accrington
Win percentage: 40.8%; Record: P409 W167 D103 L139. Photo: Lewis Storey
2. Managerless - Barnsley
Win percentage: N/A; The Tykes currently remain managerless after Poya Asbaghi’s sacking in April. Reports claim Cheltenham’s Michael Duff and Burton’s Jimmy Floyd Hasselbaink are the frontrunners to land the vacant role. Photo: George Wood
3. Ian Evatt - Bolton
Win percentage: 46.2%; Record: P106 W49 D23 L34. Photo: Charlotte Tattersall
4. Joey Barton - Bristol Rovers
Win percentage: 40.3%; Record: P72 W29 D14 L29. Photo: Harry Trump