Herein reported are the synthesis and the photocatalytic activity of MWCNT/TiO2 heterojunction photocatalysts obtained by microwave-assisted method using titanium butoxide as precursor. The obtained materials were characterized by XRD, Raman, SEM, TEM, UV-vis, FTIR, surface area (BET) and photoluminescence. The characterization results showed that the addition of MWCNT did not provide structural changes on TiO2. The photocatalytic activities of the synthesized materials were investigated using acid blue 9 dye as a model molecule. The results indicate an enhancement on photocatalytic activity by the addition of low amount of MWCNT (1 and 3 wt%). The improvement is attained to the synergic effect between TiO2 and MWCNT which reduces the electronhole pair recombination according with the photoluminescence study. In this way, a proposed schema for the enhanced photoactivity of the MWCNT/TiO2 heterojunction photocatalyst is discussed. (C) 2016 Elsevier B.V. All rights reserved.