Determining the partitioning of carbon black [CB] in miscible rubber–rubber blends [RRB’s] is a demanding problem in the rubber industry, testing one’s ability (especially tyre industry); hence, this research work aims to investigate the partitioning of CB in miscible styrene butadiene rubber [SBR]/butadiene rubber [BR] blends. SBR:BR with blend ratios of 70:30/50:50 and 30:70 with 50 phr CB were prepared on two-roll mill. Nanoscale partitioning of CB within the nanoscale phase-separated SBR/BR blends was quantitatively determined using dynamic mechanical analysis [DMA]. DMA confirmed 63%, 93%, and 45% of CB partitioning towards BR phases of 70:30, 50:50, and 30:70 in CB-filled SBR/BR blends. An attempt to determine the partitioning of CB was also made by making use of solid-state nuclear magnetic resonance spectroscopy [SS-NMR spectroscopy] to interrelate the partitioning of CB determined using DMA. TEM images were helpful in observing CB's dispersion and network ability in CB-filled SBR/BR blends. The results of CB partitioning confirm maximum partitioning of CB towards the nano-dispersed phase in CB-filled SBR/BR blends and are in well agreement with the constrained regions of BR and mechanical properties of CB-filled SBR/BR blends. Attenuated total reflectance-Fourier transform infrared spectroscopy’s (ATR-FTIR spectroscopy) spectra were used as a tool to determine the interactions within CB-filled rubbers and RRB’s in comparison to their neat counterparts. To the best of our knowledge, partitioning of CB controlled by nanoscale phase-separated morphology and its effect on mechanical properties has not been studied so far; hence, this study would be significant to academics and industrial researchers working in the area of rubber composites.