The history of Belgium’s criminal procedure is deeply related to its French heritage through its Code d’instruction criminelle of 1808 still in force nowadays. In order to portray the modern history of Belgium’s criminal procedure, this paper aims at emphasizing the evolution of the reform initiatives regarding the most symbolic aspects inherited from the French procedure: the Code of 1808 itself, the pretrial investigation focused on the juge d’instruction’s person and the emblematic popular justice of the cour d’assises. Divided into six periods from 1814 to 2020, this historical research will address and contextualize issues such as the replacement or the maintaining of the French Code, the improvement of the instruction according to its Napoleonic main features or its transformation into another type of pretrial investigation as well as the limitation or even the abolition of popular justice.