3-D velocity vectors can provide additional flow information applicable for diagnosing cardiovascular diseases e.g. by estimating the out-of-plane velocity component. A 3-D version of the Transverse Oscillation (TO) method has previously been used to obtain this information in a carotid flow phantom with constant flow. This paper presents the first in vivo measurements of the 3-D velocity vector, which were obtained over 3 cardiac cycles in the common carotid artery of a 32-year-old healthy male volunteer. Data were acquired using a Vermon 3.5 MHz 32×32 element 2-D phased array transducer and stored on the experimental scanner SARUS. The full 3-D velocity profile can be created and examined at peak-systole and end-diastole without ECG gating in two planes. Maximum out-of-plane velocities for the three peak-systoles and end-diastoles were 68.5-5.1 cm/s and 26.3-3.3 cm/s, respectively. In the longitudinal plane, average maximum peak velocity in flow direction was 65.2-14.0 cm/s at peak-systole and 33.6-4.3 cm/s at end-diastole. A commercial BK Medical ProFocus UltraView scanner using a spectral estimator gave 79.3 cm/s and 14.6 cm/s for the same volunteer. This demonstrates that real-time 3-D vector velocity imaging without ECG gating yields quantitative in vivo estimations on flow direction and magnitude.