This study systematically investigates the polymer-carbon nanotube (CNT) interaction when the interphase is tailored. Maleic anhydride-grafted-polypropylene (MA-g-PP) or polypropylene (PP) was noncovalently coated onto acid functionalized multiwall nanotube (f-MWNT) through solution mixing. These coated f-MWNTs were melt microcompounded with neat PP to form PP/f-MWNT nanocomposites. The effects of functional groups and the thin layer of solution processed polymers, namely, MA-g-PP or PP, at the PP/f-MWNT interface on crystallization and on melting behavior of matrix PP were investigated. The results were compared with a pristine MWNT (p-MWNT) incorporated system. It was shown that PP coated CNTs can serve as a strong nucleating agent for templated polymer crystal growth. Unlike other PP nanocomposites in the literature, a relatively high shift of 7 degrees C in melting peak maximum (T-p), along with a sharp melt endotherm was achieved with the addition of 0.3 wt% f-MWNT via PP/f-MWNT master batch. This indicates refinement of matrix PP crystalline region due to the tailored f-MWNT surface chemistry. With a designed self-seeding and templated crystal growth approach, columnar crystalline interphases were found surrounding MWNT which melted at 10.5 degrees C higher temperature than neat PP crystallized without undergoing the same heat treatment protocol. POLYM. ENG. SCI., 59:1570-1584 2019. (c) 2019 Society of Plastics Engineers