This study explores the challenges preservice teachers encounter: (a) in their teacher-becoming trajectory; and (b) with the implementation of social education contents in Nigeria. Understanding these is important for effective social education reforms. Narrative and observation methods were used for the study. The study drew on: (a) the stories of 37 social education preservice (SEP) teachers about their teacher-becoming trajectory and teaching practice exercise; and (b) a three-year observation of 110 SEP teachers' teaching practicum fieldworks in 12 schools to realize its objectives. Findings show professional harassment and a lack of standard learning materials as challenges social education preservice teachers encounter in their teacher-becoming. On teaching practicum, SEP teachers noted some benefits (e.g., exposure to different worldviews and nurturing of the younger generation) derived from teaching practicum; they emphasized stress, anxiety, and students' misbehaviors as challenges. SEP teachers had challenges with teaching contemporary social contents: They were oblivious of how their classroom discussions impact global issues, disregarded the sociocultural relevance of their instruction, and reproduced social issues, including political and gender problems, through their classroom practices. Guided by a sociocultural theory perspective, the study concludes with a discussion of social educators' knowledge and competency skill needs in a changing world.