This paper aims to explore how critical thinking could be fostered among secondary school students for self-realization, self-actualization, and self-reliance for sustainable development in Nigeria. This paper examines critical thinking as reflective thinking and points out some characteristics of critical thinking. The paper analyses some issues in critical thinking and contends that critical thinking could be rehabilitated in Nigerian secondary schools. The paper discusses the need for fostering critical thinking among secondary school students in Nigeria. It also indicates some of the techniques for fostering critical thinking. The paper reveals that critical thinking could help Nigerian secondary school students to be self-reliant before and after their graduation. This paper concludes that critical thinking if fostered among secondary school students in Nigeria, could launch the students into the realm of sustainable development. Keywords: Critical thinking; self-actualization; self-realization; self-reliance; sustainable development.