Travelers are now able to move between the two Eastern European countries and the rest of the EU without the need for passing through visa and passport control when traveling by sea or air.
Due to a veto by Austria, however, land routes are not included due to fears that it would enable non-EU migrants to more easily enter other EU states.
“This is a great success for both countries,” President of the European Commission Ursula von der Leyen said on Saturday.
“And a historic moment for the Schengen area the largest area of free movement in the world. Together, we are building a stronger, more united Europe for all our citizens.”
The Schengen area is comprised of the 25 other EU member states along with non-EU states Switzerland, Norway, Iceland and Liechtenstein.
Romania has said that it will carry out random checks to guard against false travel documents and and to combat human trafficking.
The two countries hope to become full members of the Schengen area by the end of the year. They are the only two EU member states not to enjoy the full Schengen benefits. Even Croatia, which joined the bloc after Romania and Bulgaria, was accepted fully into the Schengen area in January last year.