This article presents ways in which informal mentoring relationships between teachers and students can influence the emotional, behavioral, and cognitive engagement of students who are at-risk and prevent them from dropping out of school. First, a definition of informal mentoring relationships is provided, as well as a rationale for their application in secondary schools. Then, to better understand how informal mentoring relationships can help those students who are at-risk, attachment theory and brain research are used to explain why students drop out of school and what is needed to build resilience within them. Next, a theoretical model of a mentoring relationship is presented that explains the nature of emotional bonds formed between teachers and students. Strategies that teachers can use to establish themselves as informal mentors to struggling students are then provided as a way for teachers to influence student emotion and increase academic resilience. Finally, the effects of informal mentoring relationships between teachers and students on student engagement are shown in order to understand how an emotional connection with a caring teacher can lead to increases in student academic achievement.