The aim of this research was to study the impact of the unitary prevention delegates (UPDs) on the Spanish working environment. To this end, a cross-sectional study was carried out using microdata from the National Survey on Health and Safety Management in Companies (ENGE-2009) with a sample of 5147 work centres. To measure the relationship between the presence of UPD in workplaces with preventive management indicators and damage to health, individual and multiple logistic regression models were carried out, calculating the crude (cOR) and adjusted (aOR) odds ratios by sociodemographic covariates, with their corresponding 95% confidence intervals (95% CI). Ambivalent results were obtained. On the one hand, a positive impact of the UPDs was found, in the management of prevention showing a higher probability of prevention plans being carried out (aOR = 3.97; 95% CI: 3.26–4.83), risk assessments (aOR = 5.96; 95% CI: 4.44–8.01) and preventive actions were planned (aOR = 3.01; 95% CI: 2.55–3.56), as well as 1.56 times less likely to register minor occupational accidents (aOR = 0.64; 95% CI: 0.53–0.76). On the other hand, the presence of the UPDs did not promote the activation of a participatory culture and did not reduce the probability of suffering serious and fatal accidents at work. In conclusion, UPDs need to activate workers’ participation to improve results.