 After graduating law school, Moreno worked from September 1990 until January 1994 as an Associate at the law firm of Hogan & Hartson in Washington, D.C.

From January 1994 until 1995, Moreno joined the United States Department of Justice, serving as the Special Assistant to the Assistant Attorney General for the United States Department of Justice Environment and Natural Resources Division, Lois Schiffer, who held that post from 1993 until 2001.Then, Moreno served from January 1995 until January 2001 as the Counsel and then as the Principal Counsel to the Assistant Attorney General in the Environment and Natural Resources Division.From June 2001 until August 2001, Moreno served as a lawyer for Lawcorps.