There have been few reports concerning the trends in antidiabetic drug use in Japan. In 2009, a dipeptidyl peptidase-4 inhibitor (DPP4I), an antidiabetic with a new mechanism of action, was made available. This study was conducted to analyze the antidiabetic prescription trends in Japan in recent years and the influence of DPP4Is on those trends. We used monthly claims data obtained from a database company. Data from patients 20 years of age or older and who were prescribed antidiabetics were extracted and analyzed. A total of 18,457 patients were prescribed antidiabetics (mean age, 53.6 ± 11.0). The sulfonylurea prescription rate decreased while that of biguanides increased. After the introduction of DPP4Is, use of these agents rapidly increased and the rate further increased one year after DPP4I introduction. DP-P4Is also became the most prescribed antidiabetics for those prescribed antidiabetics for the first time. The decrease in the use of sulfonylureas and the increase in the use of biguanides are in accordance with trends observed in the United States and Europe, and probably reflect Japanese physicians’ awareness of cumulating evidence gained from studies such as the UK Prospective Diabetes Study (UKPDS). The rapid increase in the DPP4I prescription rate might be the result of several factors including their safety profiles, which were highlighted in clinical studies published just prior to the drugs becoming available. However, there is little data regarding the efficacy of DPP4Is in reducing diabetes related complications, which should be determined in future studies.