Fatal accidents represent a high social and economic cost to society, and many occur when workers join new companies. In Spain, 2.3% of the fatal accidents between 2009 and 2022 occurred on the first day at work in the company. This study aims to analyse fatal accidents at work in Spain on the first day of work in the period 2009–2022. A descriptive analysis of the data from occupational accident reports has been carried out. Data were collected of the Delt@ system of the Ministry of Labour and Social Economy of the Spanish Government. The variables of study were grouped into five groups: temporal, personal, business, circumstances, and fatal injury type. The study shows that fatal accidents on the first day of work occur mainly among men and in the summer months. The start of the working day and the following three hours, as well as Monday and Tuesday, have the highest number of fatal accidents. In terms of age, those aged between 40 and 59 have the highest rate. Small companies have the most fatal accidents. It is important to pay close attention to employees' first days on the job and provide them with information related with their workplace. This could increase their awareness of workplace safety from the first day.