To improve and activate the vocabulary of EFL learners, an alternative to common advice in trying to use them in speech can be invited. As two quite different methodologies in writing pedagogy are process and product writing, it is of concern to find which holds more promise for the vocabulary improvement. Product writing pedagogy encompasses accuracy-based and error-corrective tradition when students act one-off (C. Gabrielatos, personal communication, 07/29/2004), while process writing is what Raimes (1983) defines it as focused on how the writer writes, where ideas come from, how developed, and what various stages of composing involve. The initial idea is extended and refined and it is learning to write by writing. For the purpose of this study, sixtyfour from a hundred interested students at the intermediate level of English proficiency, set by a TOEFL score, pursued and consummated the weekly classes of treatment in writing instruction. A class is selected for instruction in process writing by the flip of a coin and the other taught product writing, then. After a semester period of teaching process and product writing to respective homogeneous groups and applying a pretest-posttest design, the researcher used a t-test to compare mean difference of group scores from pre-test and post-test which is a productive vocabulary test. The results of study demonstrate that process group improved their vocabulary significantly better over performance of product group, which had less than significant improvement in their scores. All subjects participated in the study are of the same age range, language proficiency level and of both sexes in balanced divisions. These factors are held constant to make a fair estimate of the role of writing method on vocabulary.