The present work checks on the efficiency of a grafted atactic polypropylene, with a high level of succinic anhydride-grafted groups, as an interfacial modifier in Polypropylene/Short Carbon Fiber composites (iPP/SCF) by mean of Dynamic Mechanic Analysis (DMA). Additionally, Differential Scanning Calorimetry to determine the crystalline content of the different materials comes in support of the DMA results. Hence, this work has been designed as an exploratory study for incoming works wherein recovered carbon fibers (rSCF) will be evaluated as reinforcement of thermoplastic composites. Consequently, we studied two different polypropylene-based composites with extreme amounts, 15% and 40% w/w, of a commercial sized SCF. Notwithstanding, just to notice that the main relaxation processes associated to the iPP matrix in the pristine composites appear sharply affected by the SCF amount, influencing also the crystalline content of the iPP matrix. The glass transition region of the iPP matrix shows significant variations well correlated with both the processing history of both the pristine iPP and the composites, and evidences the efficiency of the interfacial modifier (aPP-SA/SA) revealed as a good candidate for improving the performance in PP/rSCF composites. POLYM. ENG. SCI., 57:731-738, 2017. (c) 2017 Society of Plastics Engineers