The study aimed at understanding the relationship between the meaning in life, optimism, and pessimism among the tenth and eleventh grade students in Muscat Governorate, Sultanate of Oman. The sample of the study is 525 male and female students from the tenth and eleventh grades, (200) males and (325) females, in Muscat Governorate. The scale of the meaning in life and the scale of optimism and pessimism, and obtained the indications of validity and consistency of the scale, and the study concluded a group of results, including: - The level of meaning in life and optimism among students in the tenth and eleventh grades was high among the sample, while the results of the scale of pessimism was very low. - There are differences in the scale of meaning in life due to the gender variable in favor of females compared to males. - There are statistically significant differences in the scale of meaning in life due to the educational level of the mother. - There are statistically significant differences in the scale of optimism in favor of females compared to males. There are statistically significant differences in the pessimism scale in favor of males compared to females. - There are significant differences in the level of optimism and pessimism due to the level of academic achievement of students. - There are significant differences in the level of optimism and pessimism due to the educational level of the father. - There are significant differences in the level of optimism and pessimism due to the educational level of the mother. - There is a positive correlative relationship between degrees of meaning in life and degrees of optimism, while there is a negative correlative relationship between degrees of meaning in life and degrees of pessimism. There is a statistically significant effect of meaning in life variable on the prediction of optimism among the tenth and eleventh grade students in Muscat Governorate schools. - There is a statistically significant effect of meaning in life variable on the prediction of reducing pessimism among the tenth and eleventh grade students in Muscat Governorate schools.