This study aimed to show the efficacy of morphological analysis as a vocabulary-developing strategy that enables students to decode or determine the meanings of vocabulary, to enlarge vocabulary and to retain vocabulary in long-term memory. The study was a one-group pre-test-post-test experiment and investigated the effect of morphological analysis on the vocabulary-developing ability of 40 Bangkok University students and explored their attitudes towards the use of morphological analysis. The instruments were a vocabulary test and a questionnaire exploring their attitudes toward morphological analysis. The pre-test and post-test scores of the experimental group were calculated by descriptive statistics and compared using a dependent t-test measure. It was found that the students obtained higher scores on the post-test than on the pre-test at 0.05 level of significance. In addition, their attitudes towards using morphological analysis were enthusiastic. Moreover, the results of this study suggested that using morphological analysis assisted the students in decoding the meanings of vocabulary and enlarging vocabulary, helped them to retain vocabulary in long-term memory, motivated them to learn the English language and gave them pleasure in learning vocabulary. Pedagogical implications for vocabulary learning are suggested in the conclusion.