Fabrication of Sn-MWCNT composite layer through reflow of Sn-decorated MWCNT powder was conducted in this study. Commercially available MWCNTs were oxidized by using K2Cr2O7 / H2SO4 solution for the surface modification. The oxidized MWCNTs were dispersed in SnCL / HCl solution and subsequently a reducing agent NaBH4 was introduced to form crystalline Sn. During the Sn reduction process, 1,10-phenanthroline capping agent was introduced to control the particle shape and size. It was found that SnO2 nanoparticles on the surface of MWCNTs and crystalline Sn particles were obtained simultaneously through the chemical reduction reaction. When 1,10-phenanthroline was used, Sn particles had spherical shape and uniform size compared to the one without 1,10-phenanthroline. Afterwards, the Sn-MWCNT powders were mixed with a flux to form a paste for a wetting test on a Cu substrate. After a reflow step of the paste, Sn-MWCNT composite layer could be formed showing no separation between MWCNTs and Sn by bonding of molten Sn to SnO2 nanoparticles on the surface of MWCNTs.