We propose a novel and minimal framework where a light scalar field can give rise to dark matter (DM) self-interactions, while enhancing the CP asymmetry required for successful baryon asymmetry of the Universe via leptogenesis route. For demonstration purpose we choose to work in a scotogenic seesaw scenario where the lightest among the right-handed neutrinos (RHN), introduced for generating light neutrino masses radiatively, play the role of DM while the heavier two can play nontrivial roles in generating DM relic as well as lepton asymmetry. While dark matter self-interactions mediated by an additional singlet scalar can alleviate the small scale issues of cold dark matter paradigm, the same scalar can give rise to new one-loop decay processes of heavy RHN into standard model leptons providing an enhanced contribution to CP asymmetry, even with sub-TeV scale RHN mass. The thermally underabundant relic of DM due to large annihilation rates into its light mediator receives a late nonthermal contribution from a heavier RHN. With only five new particles involved in the scotogenic seesaw, each having nontrivial roles in generating DM relic and baryon asymmetry, the model can explain nonzero neutrino mass while being verifiable at different experiments related to DM direct detection, flavor physics, and colliders. The mechanism we demonstrated here by using a scotogenic seesaw scenario is also applicable to other models. © 2022 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the "https://creativecommons.org/licenses/by/4.0/"Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP3.