Contextual Vocabulary acquisition is a kind of learning the new words through guessing of the meaning for an unknown word within the text. The main purpose of this study was to investigate the effectiveness of a contextual guessing strategy on vocabulary learning at the intermediate level .contextual guessing strategy is to guess the meaning of vocabularies with the help of surrounding words in the context without any translation. This paper reports the findings of a two qualitative studies which carried out in Kavosh foreign language institute level INT2 Twenty male and female students were selected and assigned to ’context’ and ‘non-context’ groups. The context group received an instruction to infer the meaning new words while the non-context participants were treated by learning new vocabularies individually. The results indicate that contextual guessing strategy was more effective vs. a list of isolated words instruction regards being remained in long term memory.