The study aimed to identify the optimism and pessimism and its relationship with self- concept among the diploma students in schools from Wilayat Nakhal and Wilayat Barka, province of South Batinah, Sultanate of Oman. The study sample consisted of (195) students, chosen randomly through stratified sample from above mentioned schools. The study used two scales: the Arab scale of optimism and pessimism; which originally designed by Ahmed Abdel-Khalek (1996), consisting of two separate sub- scales: (1) the measure of optimism consisting of (15) items, and, (2) the measure of pessimism consisting of (15) items. The other scale used in this study is the "Self-Concept" scale used by Aisha Khalfan Al-Wihaibi (2009), and originally designed by Mohammed Emad El-Din Ismail (1986), consisting of (91) items. The indicators of validity in both measuring tools where determined by using two ways: validity of statements through using the method of arbitration, and structure validity. In addition, the reliability of scales were further examined through the indicators of stability measurements by Cronbach' alpha, reaching a reliability coefficient of optimism (0.853), while the reliability coefficient of pessimism (0.869). On the other hand, the reliability coefficient of self-concept reached (0.951). The statistical package (SPSS) was used to analyze the collected data. The study showed the following results: 1. The level of optimism is high, while the level of pessimism among students in general education diploma, province of South Batinah is low. 2. The level of self-concept among students in general education diploma province of South Batinah is high. 3. There is a negative correlation between optimism and self-concept, and a positive correlation between pessimism and self- concept. 4. There are no statistically significant differences in optimism and pessimism due to the variable of gender and geographical location, while statistically significant differences exist in optimism depending on the interaction between gender and geographical location. 5. There are statistically significant differences in self-concept according to the variable of gender in favor of males, while these differences did not appear in the variable geographic location, or the interaction between gender and geographical location. In light of these results, a number of recommendations were suggested, including: introducing courses in the curriculum of the General Education Diploma schools that include topics developing the concepts of optimism and self-concept, as well as providing Resource Learning Centers with books that encourage students to be optimistic about life and the future.