Patients with myelodysplastic syndrome (MDS) receiving hypomethylating agents commonly develop thrombocytopenia. This double-blind study evaluated the efficacy and safety of romiplostim, a peptibody protein that increases platelets, in patients with MDS receiving decitabine. Patients received romiplostim 750 μg (n = 15) or placebo (n = 14) and decitabine. Median platelet counts at the beginning of each decitabine cycle trended lower in placebo-treated than in romiplostim-treated patients. Bleeding events occurred in 43% of placebo-treated and 27% of romiplostim-treated patients, and platelet transfusions were administered to 57% of placebo-treated and 47% of romiplostim-treated patients. Overall clinical therapeutic response was achieved by 21% of placebo-treated and 33% of romiplostim-treated patients. Treatment was generally well tolerated. Progression to acute myeloid leukemia (AML) occurred in one patient per group. Adding romiplostim to decitabine treatment is well tolerated and may be beneficial, as indicated by trends toward higher platelet counts at the beginning of each treatment cycle and lower platelet transfusion rates and percentages of patients with bleeding events.