Poly (ether-ether ketone) (PEEK) is one of the most versatile engineering thermoplastics; it has been widely used in aircraft, telecommunications and medical applications due to its high thermal and chemical stabilities. Its use as a bone implant with and without fillers has also been largely studied. Multiwall carbon nanotubes (MWCNT) has also the same widespread applications. However, the combination of both materials as a nanocomposite has been less studied, probably due to the incompatibility between both surfaces. In this work, MWCNT (Nanocyl, NC 7000, d= 9.5 nm, 90% purity)) were chemically treated to enhance their interactions with the PEEK (Rhodia Solvay, KetaSpire KT-851) surface. Two treatments were made: oxidation with HNO3 (o-MWCNT) and silane grafting (s-MWCNT). The silane was m-aminophenyltrimethoxysilane (Oakwood, S00700). The introduction of –COOH groups on the MWCNT surface was analyzed by UV-vis (Perkin Elmer Lambda EZ 210) by the observation of the 256 nm peak, while the silanization was studied by FTIR( ThermoScientific, modelo Nicolet 6700, ATR mode). Nanocomposites of 0.5, 1 and 2 wt% of both types of MWCNT were prepared by melt mixing in a rheometer Haake, Rheomix 3000p, at 360°C, 70 rpm, during 8 min. The steady state and oscillatory rheological properties were measured in an AR-G2 stress controlled rheometer (TA Instruments) using parallel plates geometry (25 mm, gap=1mm) at 360 oC. The dynamic mechanical properties were measured in a DMA Q800 (TA Instruments), using a single cantilever geometry, between 30 and 280 oC, at 1 Hz and a heating rate of 3 oC/min. The influence of the MWCNT surface treatment was observed by the increasing of the shear viscosity and storage moduli (o- and s-MWCNT) and the glass transition temperatures (o-MWCNT), probably due to an increase interaction between the –COOH surface groups of the MWCNT and the –C=O groups of the PEEK.