Industrial automation systems are becoming increasingly sophisticated due to increasing requirements complexity, including operating in distributed environments, typical of Industry 4.0. This complexity in systems has been addressed through system modeling tools with advanced capabilities of simulation of processes and controllers and visual animation, enhancing the interactivity and involvement of operators and users, contributing to improving the performance of these systems. Several simulation environments, developed by some manufacturers, can test PLC programs written in IEC 61131–3 languages but have the counterpart of being expensive or difficult to access. This research work presents an approach for developing a platform for simulating industrial processes and virtual PLCs. This approach is based on a Structured Text IEC-like Language Interpreter, systems simulation, and Unity 3D game engine. The developed platform can recognize structured text (ST) and validate its syntax through a lexical and syntactical analyzer using the Flex and Bison tools. As an illustration, a client application has been developed in Java. Users can enter their Structured Text code, execute it on a virtual PLC, declare input/output addresses, analog or digital, and observe their state. The integration of game engines has allowed obtaining a simulation system that meets more demanding requirements in modeling automation and control systems using open-source tools.