The present interdisciplinary research investigates the differential emotional expression between Persian monolinguals and Persian-English bilinguals. In other words, the article was an attempt to answer the questions whether bilinguals and monolinguals differ in the expression of positive and negative emotions elicited through sad and happy autobiographies and measured through UWIST Mood Adjective Checklist. The result of this pioneering work indicated no significant difference between Persian monolinguals and Persian-English bilinguals in expressing happy memories while differences were observed on sad memories. Bilinguals expressed more negative emotions in their L2 than L1. This outcome support the dominant claim that second language is the preferred language for the expression of sad emotions since it is the language of emotional detachment and distance. Further analysis on the number of words bilinguals and monolinguals used to express both sad and happy autobiographies indicated that bilinguals used more words in expressing both sad and happy autobiographies.