Blockade of programmed cell death ligand‐1 with durvalumab has shown efficacy and safety in large, international studies of patients with advanced solid tumors. A phase 1, non‐randomized, open‐label multicenter study was initiated to evaluate durvalumab in a Japanese population. The first part of this study used a standard 3 + 3 dose‐escalation design to determine the optimal dosing schedule of durvalumab. Primary objective was evaluation of safety and tolerability of durvalumab monotherapy. Secondary objectives were to evaluate maximum tolerated dose (
MTD
), immunogenicity, pharmacokinetics, and efficacy. Twenty‐two patients (median age, 61.5 years; range, 41‐76; 64% male) received durvalumab at doses of 1, 3, or 10 mg/kg every 2 weeks (q2w), 15 mg/kg q3w, or 20 mg/kg q4w. Twenty patients discontinued before completing 12 months of treatment as a result of progressive disease and two due to adverse events (
AE
). The most common treatment‐related
AE
(tr
AE
) were rash (18%) and pruritus (14%); two patients had grade ≥3 tr
AE
including one patient each with hyponatremia and hypothyroidism. No patient experienced a dose‐limiting toxicity (
DLT
) during the
DLT
evaluation period and the
MTD
was not identified. There were no
AE
leading to a fatal outcome during study treatment. Durvalumab showed dose‐proportional pharmacokinetics across the 1‐20 mg/kg dose range; incidence of positive titers for antidrug antibodies was 9%. One patient with lung cancer had a partial response and disease control rate at 12 weeks was 36%. In conclusion, durvalumab at the doses and regimens evaluated was safe and well tolerated in Japanese patients with advanced solid tumors.