Intrinsic motivation is an important aspect that needs to be assessed and boast for EFL learners because it is believed that students with high levels of intrinsic motivation behave productively in the class, work harder outside the class, and persist longer with the achievement of vocabulary. On the contrary, students with low levels of intrinsic motivation become frustrated and disappointed with learning vocabulary with themselves resulting in hindrance in grasping the vocabulary learning strategy and performing its tasks. Therefore, the present study aimed at investigating the relationship between EFL young learners’ achievement of vocabulary and their intrinsic motivation. The study sample consisted of fifty-six second year prep school students at Azza Zidan Official Language School, Fayoum Governorate, Egypt. Students’ achievement of vocabulary was assessed using a vocabulary achievement test and their intrinsic motivation had been rated using 5 points Likert scale, both prepared by the researcher. The content validity of items in the test was verified by experts in the field of the curricula and EFL instruction. Besides, the statistical package for social sciences (SPSS) was used for analyzing the data obtained, the total correlation of the items was determined, and correlation measurements between subtitles and the total points of the scale were also performed. Also, Cronbach’s alpha coefficient test was applied to determine the test reliability. To define the internal consistency and reliability of the test, the alpha test focused on subtitles in particular. After these analyses, the results of the study sample showed a statistically significant positive correlation between the scores obtained from the vocabulary achievement test regarding the intrinsic motivation scale.   Keywords: Vocabulary Achievement, Intrinsic Motivation, Young Learners.