Tracking detectors for the future hadronic machines are expected to stand an extreme level of radiation and to provide at the same time high space and time resolutions. Diamond detectors satisfy both of the latter requirements and, in addition, a 3D geometry with thin columnar resistive electrodes orthogonal to the diamond surface enhances the natural radiation tolerance and response speed of this material. We report on the timing characterization of a 3D pixel diamond detector prototype fabricated, by laser graphitization with a 55 × 55 μm2 pixel geometry, in Firenze. Results of a tests beam provide a time resolution well below 100 ps with an efficiency larger than 99%.