Occupational accidents cause serious consequences. Providing first aid (FA) in the workplace can reverse unpleasant results. Aim of our study was to evaluate the knowledge on FA of industry workers through a questionnaire. Our sample constituted of 236 workers, 40 (Group A) were trained on FA by a team of doctors authorised by the Hellenic National Centre of Emergency Help, while 196 had never have a formal training on FA (Group B). In Group A the mean value of correct answers (performance score) was higher than Group B (62.7 and 50.4 respectively), while the total sample of workers ranged from 21.1 to 84.2. Group A replied correctly about normal values (NVs) of pulse, arterial blood pressure (BP) and breaths at 67.5%, 35% and 47.5% respectively. Group B replied at 32.8%, 18.4% and 30.6% on the corresponding NVs. In Group A, 95% answered properly about the definition of Cardiopulmonary Rehabilitation (CPR) but only 25% were acquaint with the necessary number of chest compressions and 32.5% with the number of necessary mouth-to-mouth ventilations to practice in case of CPR. In Group B, the corresponding percentages were 72.4%, 26% and 36.7%. Only 5% from Group A and 1% from Group B answer correctly and simultaneously about estimation of vital signs and CPR practice. In conclusion, the vast majority of workers are unable to provide efficient FA as long as they can't estimate vital signs and provide satisfactory CPR.