The Belgium-born midfielder has earned himself a transfer to the San Paolo outfit with his good performances in Serie B last term
The Partenopei were keen to add some more depth to their squad ahead of the start of the 2012-13season, and head coach Walter Mazzarri has now got the midfield reinforcements he desired.
"El Kaddouri is an important player for now and for the future," Napoli president Aurelio De Laurentiis commented on the move.
"It took me only one minute to agree terms with Brescia president Gino Corioni and another minute to reach an agreement with his agent Mino Raiola. I have always worked well with Mino because he's an excellent professional."
The 22-year-old midfielder came through the ranks of the Anderlecht youth academy, but left the club in the summer of 2008.
El Kaddouri had since made over 60 official appearances, and will now continue his career in southern Italy.