Mosaffa was born in Tehran, Iran. His father, Mozaher Mosaffa is a renowned Persian poet and professor of Persian literature at the University of Tehran (UT). Mosaffa's mother, Amir Banoo Karimi is also a leading scholar and professor of Persian literature at the University of Tehran (UT) and the eldest daughter of the legendary Persian poet, Amiri Firuzkuhi.
As a child, Mosaffa discovered his interest in story writing and english, contributing to his fluency in the language. He is a graduate of Civil Engineering from the University of Tehran (UT) where he showed an interest in acting; making his debut in the 1991 film, Omid. Mosaffa went on to win the prize for best male actor the following year at the Fajr International Film Festival for his role in Darius Mehrjui's film, Pari. Mosaffa met his future wife, Iranian actress Leila Hatami on the set of Dariush Mehrjui's 1996 film, Leila. The two married in 1999 and have two children, a son named Mani (born February 2007) and a daughter named Asal (born October 2008).
Mosaffa's experience with directing began with the short films, Incubus, The Neighbor and the documentary feature, Farib-e-She'r or The Deceit of Poesy. He then went on to direct his first film in 2005 with Portrait of a Lady Far Away /Sima-ye Zani Dar Doordast, starring Leila Hatami and Homayoun Ershadi which was awarded the Sutherland Trophy at the BFI London Film Festival also known as the London Film Festival. His first feature film subsequently won the hearts of the audience winning the People's Choice Award at the Chicago International Film Festival and was nominated for the Crystal Globe at the 2005 Karlovy Vary International Film Festival. Mosaffa's second film, The Last Step /Pele ye Akhar, starring Leila Hatami has received acclaim from critics and audiences worldwide following its international premiere at the 2012 Karlovy Vary International Film Festival which gained Mosaffa the international critics' FIPRESCI prize for best film and awarded Leila Hatami with the Crystal Globe for Best Actress for her leading role in the film.
In October 2012, Mosaffa joined Oscar winning director of A Separation, Asghar Farhadi in Paris; starring alongside Bérénice Bejo and Tahar Rahim for Farhadi's first foreign language film, "Le Passé" or "The Past" set to premiere at the Cannes Film Festival in May 2013.
