This research aimed 1) to study effectiveness index (E.I) of English vocabulary learning ability of Sathid Grade 5 students by using games, 2) to compare the students’ English vocabulary learning ability before and after learning by using games, and 3) to study the student’s English vocabulary retention. The target group in this study consisted of 39 students in grade 5 of Sathid Primary School, chosen by purposive sampling. The research instruments were 5 lessons, 30 achievement learning tests, and a test of vocabulary learning retention test containing 30 items. The statistics used to analyze data were percentage, mean, standard deviation, deviation and paired-sample t-test. The research results were found as follows: 1) The effectiveness index (EI) of the English vocabulary learning ability of Sathid Grade 5 students by using games was 0.536, meaning that students’ ability was higher at 53.60% 2) The students’ ability to learn English vocabulary learning by using games when compared to The pre-posttest after studying was significantly higher than before. The posttest Scores were significantly higher than the pretest scores at the .05 level of significance. The mean score after the study was 23.97 with a standard deviation of 3.63, and the The mean score before the study was 17.18 with a standard deviation of 5.69. 3) Students had higher ability to learn English vocabulary immediately after learning than after 14 days of learning by using games, with a significance at the .05 level.