The Blues boss revealed the homegrown keeper will be given his chance to stake for first-team inclusion.
Pompey’s number one spot is up for grabs next season, following Gavin Bazunu’s return to Manchester City after a fantastic season on loan at Fratton Park.
Cowley has to weigh up whether Bass is ready to assume that role, as he enters the final year of his existing agreement.
The 24-year-old spent the second half of the season on loan at Bradford City, where he gained some good experience picking up 21 appearances.
Bass has been linked with the Bantams’ League Two rivals Hartlepool this summer, with his future still unclear.
Cowley has held talks with the academy graduate after his return from Valley Parade about the path ahead.
The immediate route for Bass is to return for pre-season training along with the rest of his team-mates on June 20.
Cowley will then assess the former Southend loanee, before making a call about the longer term picture.
He said: ‘Alex and I have had a chat off the back of the season ending.
‘We had a good conversation about what has been for him this season.
‘The plan for him will be to rejoin the group at the beginning of pre-season and we will take things from there.’
Bass is the only senior keeper currently at Pompey, with Bazunu leaving and Ollie Webber’s services not retained after arriving from Crystal Palace in January.
Emerging youngster Toby Steward has been handed a senior contract and will join the first-team group next month.
Bass has certainly gained experience this term with his stint at Bradford City.
That followed on from a difficult 2020-21 season in which a broken leg restricted his game time to just six appearances.
Those issues are now firmly behind him, however, with Bass now having 63 senior appearances to his name since making his debut at Coventry City in the EFL Cup back in 2016.
Cowley is clear the Bradford experience was beneficial for Bass.
He said: ‘Alex has ended up playing 28 games, which was a real step in the right direction for him.
‘That has come off the back of a season when injury really restricted him to a small amount of games.
‘He’s definitely better for that experience with Bradford.’