Candidate of Judicial Sciences and Reserve Lieutenant, and after dissertation of his thesis and obtaining of a degree, he was appointed assistant at YSU Chair of Civil Law.

[1] From 2002 to 2005, Petrosyan served as the head of the Department of Social Sciences at Vanadzor State University.

Between those years, since 2003, he also served as associate professor of the Faculty of Law and the Chair of Civic Procedure of Yerevan State University and between 2004 and 2005, worked as Advisor to the Head of the Community at Nor Nork District, promoting soon after to the Chief of Staff position.

From 2005 to 2009, Petrosyan served as jurist to the Direct General at Veon Armenia CJSC, and later as senior expert on Labor Law Affairs.

Between 2007 and 2008, he worked as Head of the Legal Supervision Department at the Audit Chamber of Armenia.