This study aimed to clarify the effect of using Frank Lester model on mathematical problem solving and math anxiety of eleventh-grade students and tried to answer the following two questions: 1. What is the effect of using Frank Lester model on mathematical problem solving of eleventh-grade students? 2. What is the effect of using Frank Lester model on math anxiety of eleventh-grade students? To answer these questions, a sample of (62) eleventh-grade students was chosen and divided into two groups: an experimental group with (30) students, studied using Frank Lester model, and a control group with (32) students, studied using the usual way. To attain the purpose of the study, an educational material for the unit of "Sequences and Series" of grade eleven was prepared according to Frank Lester model. Also, a mathematical problem solving test and a math anxiety scale were applied. The study result showed statistically significant differences at the level (a=0,05) between the mean score of the experimental group and the mean score of the control group in the mathematical problem solving test and math anxiety scale in favour of the experimental group who studied using Frank Lester model. In light of these results, the study recommended the importance of developing students' problem solving skills, and providing appropriate and encouraging study environment to improve students' spirit and reduce their math anxiety.