Cardoso, who has earned eight caps for Luxembourg, made 23 appearances for Borussia Monchengladbach's second team in the Regionalliga West last season. The loan move is designed to accelerate his development by giving him regular first-team football in a competitive league environment.
Sporting director Rouven Schröder outlined the reasoning behind the move.
"Tiago is an established part of the Luxembourg national team and has already demonstrated his Bundesliga quality with us at a young age," Schröder said.
"This is therefore a logical and important next step for him to gain playing experience in a strong league for a year.
"We have had very good experiences with this approach in the past, especially with goalkeepers, and we hope to see that important next step in his development in this case too."
The move reflects Gladbach's established pathway for young goalkeepers, with the club having successfully used loans abroad to develop players at this stage of their careers before reintegrating them into the first-team setup.
RAAL La Louvière finished their most recent Belgian first division campaign in mid-table, giving Cardoso a realistic prospect of regular minutes without the pressure of a relegation fight or title race. For a young goalkeeper still establishing himself, the environment is well suited to consistent development.
Gladbach retain his registration and expect him to return with a full season of senior first-team football behind him — experience the club believes will accelerate his readiness for Bundesliga competition.
The loan is a further sign of the club's commitment to a long-term development pathway for Cardoso, who has established himself as a regular in the Luxembourg national side despite his young age.