In this work an integrated tunable optofluidic liquid core-liquid cladding (L2) optical fiber is presented. The device has been realized by exploiting an innovative three-dimensional hydrodynamic focusing scheme. A tunable circular liquid core has been obtained that is located in the center of the channel, regardless of the flow rate ratio of the cladding and core liquids. This circular geometry allows a more simple control of the optical property of the beam and the input and output coupling with standard optical fiber. A liquid core with a tunable diameter ranging from 45.3 to 11.2 mu m has been successfully obtained.