Ultrasound-guided vascular access is practiced widely. Optimal educational methods have not yet been established. We hypothesized that a step-by-step web-based learning system is effective for self-learning. In this study, we examined the potential of this system as a self-learning tool. This was an observational study at a single institution. Participants included residents, who were self-educated through the web-based system. Skill proficiency was measured after self-learning. The primary outcome was the extent to which self-learning enabled residents to acquire proficiency in the basic skills of ultrasound-guided vascular access: needle visualization, hand-eye coordination, and avoiding posterior wall penetration. A secondary outcome was the time required to achieve proficiency. Thirty-nine residents were enrolled in this study. Eleven residents (28%) passed the first skill assessment test. There was no significant difference in the number of days that the web-based system was accessed, the total number of screen views, or the total learning time between participants who passed and those who failed the first test. Skill assessment scores between those who passed and those who failed the first test were different, especially the score for hand-eye coordination, and the number of posterior wall penetrations. Self-learning with a web-based system enabled 28% of residents to pass the first skill assessment test. The remaining 72% failed the first skill assessment test but continued to learn using the web-based system and eventually passed the test. Hence, the web-based system needed formative testing to function as a self-learning system. Simulation education for vascular access is expected to increase in educational content and methods. Self-learning through a web-based learning system is a leading candidate for this growth.