Poor vocabulary retention is one of the major difficulties experienced by English as a foreign (second) language (EFL/ESL) students. To tackle this problem, the current study explored the impacts of the modified visual input and the modified oral input on the short-term and long-term vocabulary retention of Iranian EFL students and their perceptions regarding implementing these two types of input in their classes. The initial population consisted of 90 male and female students from Islamic Azad University, Science and Research Branch in Tehran, Iran. The convenience sampling method was implemented to select the participants. After administering the Oxford Placement Test (OPT), 60 students were chosen to serve as the participants, and they were randomly divided into two groups of 30 learners, namely the experimental groups A and B, which received instructions based on the modified visual input and the modified oral input, respectively. Later, the participants received ten 60-minute treatment sessions. Next, the learners' short-term vocabulary retention was assessed using the same vocabulary test as the posttest. One month later, the same test was given to students to check their long-term vocabulary retention as the delayed posttest. The results showed that the two types of input had significant impacts on the vocabulary short-term and long-term retention of the Iranian EFL students to varying degrees. Moreover, the qualitative findings indicated that the learners adopted a significantly positive view toward implementing oral and visual input modifications in their classes. In the end, the implications of the study are provided.
