Turkish and US law, in both, there is a presupposition that joint (criminal) trials is advantageous for both judicial institutions and decision-makers, as well as for the defendants. However, violations of the defendant’s basic judicial rights that arise in multi-defendant trials, such as those involving organized crime, have called into question the acceptance that joint trials should be a procedural tool used in all cases. Nevertheless, it is also considered that this presupposition is not always accurate regarding the efficient functioning of justice mechanisms. This study compares the regulation and application of joint trials in Turkish criminal procedure law and US federal criminal procedure law.