In recent years, eco-driving has proven to be an effective tool for reducing fuel consumption and greenhouse gas (GHG) emissions. Until now, most research carried out has focused on ordinary drivers applying eco-driving techniques on their usual routes. However, there is little research on professional driver couriers. This research is aimed at analyzing the effects that eco-driving has on fuel consumption and GHG emissions on courier deliveries in small cities such as Caceres (Spain). For this purpose, a real-life experiment was performed with professional drivers with Spanish post vans from the public sector company Correos. In the first period, driving was under normal conditions (non-eco), and after a theoretical training eco-driving course, there was a second driving period (eco). Driving parameters (speeds, accelerations, rpm, and consumptions) were recorded on all trips to analyze how effective the eco-driving was. The research concluded that eco-driving training does not correlate with more sustainable driving for professional drivers under pressure with the need to deliver packages on time. However, there is a trend in fuel savings when using higher capacity routes.