This study aims to detect differences in the features of the proposed and supported projects for different priority technology areas (PTAs) of the TUBITAK Prioritized Areas R&D Grant Program together with the analysis on the output, input, and behavioral additionality of the supported projects. Non-existence of a previous study on the evaluation of the Prioritized Grant Program of TUBITAK contributes to the originality of this study in addition to being one of the limited examples about the studies on the efficient allocation of R&D incentives in the literature. During this study, firstly, descriptive statistics of program indicators is analyzed. Then, the relationship between output amount and the characteristics of the supported projects and their calls is estimated for different PTAs by the Ordinary Least Square (OLS) method. Moreover, interviews involving questions to measure output, behavioral and input additionalities are also conducted with a sample of supported project coordinators. Using both quantitative and qualitative methods together, not seen in the literature frequently, increases reliability and originality of the study. Consequently, it is detected that the amount of proposed and supported projects and average requested and given fund per project differ with PTAs and project characteristics. Additionally, the effects of these characteristics on output amount differentiate with PTAs. Moreover, supported projects and their outputs are inadequate to meet the specific targets of the grant program despite their significant project and input additionalities. Some policies, which could be helpful to increase the effectiveness and efficiency of the Program are recommended as a conclusion of this study.