The purpose of this research was to design and evaluate a web-based self-learning environment for historical inquiry embedded with different types of instructional support featuring story-based pedagogical agents. This research focused on designing a learning environment by integrating story-based instruction and pedagogical agents as a means to deliver the problem context and learning tasks as well as to embed instructional support in an engaging way. Versions of the lesson modules were designed and tested iteratively to determine the impact of pedagogical agents on learners' performances and perceptions regarding the inquiry learning activity. A design research approach applying a mixed study of quantitative and qualitative research methods was taken. Quantitative and qualitative data in terms of student performances and perceptions of the learning activity were collected through the four rounds of experiments. A multiple-choice comprehension test and essay writing test were assigned to detect different levels of learning performance, and learners' perceptions were collected through a self-report questionnaire. The initial study indicated that the story elements and mediation of the pedagogical agent did not have an impact on learning performance, although they succeeded in gaining the interest and enjoyment of learners. The instructional supports were modified to enhance learning performance by providing examples, domain heuristics, and practice opportunities through the interactions with the mentor and peer learner agents. As a result, while the impact on student enjoyment, interest, and attention held steady, significantly more students delivered situational arguments using multiple perspectives than did those in the control condition. It was also found in the following study that more difficult exercises lacking adequate instructional support may hinder learning performance. A notable finding of this research was that the use of story-based pedagogical agents impacted students' ways of interpreting historical sources and making arguments, which was observed in the essay writing task. As previous studies on pedagogical agents have not performed this type of measurement, this study contributed a novel finding. The result also suggested that the story elements have to be incorporated with necessary instructional design considerations in order to foster learning performance while sustaining student interest in the learning activity. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]