This study examines the role of self-development as a mediating variable for the relationship between human error and service effectiveness in the public sector. Lately, the public service sector has become a particular concern because the public feels it is still inadequate and meets expectations. This research was conducted at the trade office of South Sumatra Province, INDONESIA. The survey was conducted on 150 respondents who were taken at random simply. Data analysis techniques are carried out with a structural equation model (SEM) approach. The results showed that Human error negatively affected the effectiveness of services at the Southern Sumatra Regional Trade Office. The existence of employee self-development has weakened the relationship between Human Error and service effectiveness. Through self-development on employee personal factors, work experience, and taking advantage of opportunities in the environment can reduce the role of human error on service effectiveness. Management should provide support and recognition to employees who seek to develop themselves and improve the quality of service. This can motivate employees to continuously improve their performance and contribute positively to the organization's effectiveness. More skilled and confident employees tend to have a better ability to overcome or compensate for mistakes. Self-development can be crucial in building an organizational culture more open to learning and improvement. Employees encouraged to continue developing themselves tend to be more open to receiving constructive feedback and learning from their mistakes and those of others. This can create an environment where mistakes are seen as opportunities to grow and improve, not as signs of failure.