The objective of the study was to analyse the effectiveness of training provided to employees in a catering company with implemented food safety management system pursuant to ISO standard of 22000 series and to determine the risk of making mistakes by those employees when fulfilling their on-the-job duties owing to insufficient assimilation of the knowledge introduced during the training. The study allowed the verification of the level of employees’ knowledge in the company prior to and after the training. The acceptable risk of mistakes made by the employees in the catering company with the implemented food safety management system pursuant to the ISO standard of 22000 series was proved exclusively with the reference to the employees employed as cooks. The statistical analysis (using a chi-square test) confirmed the statistically significant relationships to exist between the increase in knowledge and the job position in the company. The applied risk assessment proved to be a useful method to analyze the results of staff training effectiveness for it enhanced the drawing of conclusions by means of statistical methods. It was proved that staff trainings played a significant role in the upskilling of the catering employees and in the minimizing of risk of their making mistakes.