In this paper, a new kind of nanohybrid poly(tetradecyl methyl-acrylate)-graphene oxide (PMA(14)-GO) as pour point depressant (PPD) was prepared from graphene oxide, using matrix via in situ free radical polymerization. The effect of PMA(14)-GO (i.e., PMA(14)-3GO, PMA(14)-6GO and PMA(14)-9GO) PPDs on the cold flow properties and exhaust gas emissions of diesel fuels were studied. Results indicated that PMA(14)-GO PPDs exhibited a better effect on cold filter plugging point (CFPP) and solidifying point (SP) than that of PMA(14). Among them, PMA(14)-6GO and PMA(14)-9GO were the most suitable candidates for improving CFPP and SP. Specifically, upon addition of 0.2 wt% PMA(14)-6GO could reduce the CFPP of diesel by 14 degrees C, and 0.2 wt% PMA(14)-9GO reduced the SP of diesel by 19 degrees C. Moreover, PMA(14)-GO PPDs could effectively lower the low-temperature. Other fuel properties were also determined and compared with the ASTM D975. Given the heterogeneous nucleation mechanism, uniform and tiny particle-shaped crystals were observed by polarizing optical microscopy and differential scanning calorimetry. In addition, burning diesel fuel with PMA(14)-GO PPDs effectively reduced HC and CO emissions, whereas NO and CO2 emissions increased with the increased engine speed at full load.