This corpus-based study investigated hand-written argumentative essays versus ChatGPT-generated essays written by two groups of EFL Saudi undergraduate business students. The aim was to compare the use of circumstances and processes and their associated participants, employing Halliday's (2014) Systemic Functional Linguistics framework. Since students rely on ChatGPT in writing, examining how the integration of ChatGPT influences their linguistic choices is pertinent. Identifying the most common transitivity process used in students’ writing would contribute to pedagogical interventions that improve students’ writing abilities and foster successful communication. Thirty-eight Saudi EFL undergraduate business students were randomly selected from the English Language Skills Department, Common First Year, King Saud University. The study used an experimental design with a control group and an experimental group. The participants were required to write an argumentative essay about whether or not money is a true indicator of the success of a business. Nineteen of the participants used ChatGPT as a tool in writing, and the other half did not. To calculate the number of clauses, the UAM Corpus Tool was used and the transitivity analysis was done manually. Results showed that the relational process was the most frequently used transitivity process in the control group essays. The participants identified and described the concepts they mentioned while writing. However, the material process was the experimental group’s most frequently used transitivity process. The participants referred to their experiences while getting information from ChatGPT, leading them to use the material process. The current study focused on providing valuable insights into undergraduate business students’ writing. Further studies can investigate different levels of students and other types of essays using ChatGPT.