We evaluated a novel, sled‐mounted needle guide for ultrasound‐guided vessel cannulation. Fifty medical students were randomly assigned to use ultrasound with the sled (sled group, n = 23) or ultrasound without the sled (control group, n = 27) for vessel cannulation in a phantom. For each of 15 attempts we recorded cannulation time and designated a successful cannulation as 1 and a failure as 0. Our primary outcome was the mean overall success rate. The median (IQR [range]) number of successes in the sled group and control group were 15.0 (13.0–15.0 [11.0–15.0]) and 11.0 (9.0–13.0 [6.0–15.0]), respectively (p < 0.001). Cannulation time decreased from the first to the last attempt in the sled group from 7.0 s (6.0–10.0 [4.0–16]) s to 4.0 s (3.0–4.0 [1.0–6.0]) s and in the control group from 35.0 s (27.0–35.0 [11.0–35.0]) s to 7.0 s (5.0–10.0 [3.0–25.0]) s. The sled group demonstrated a shorter cannulation time at each attempt (p < 0.001). The novel sled improved the success rate and efficiency of ultrasound‐guided phantom vessel cannulation.