Two commonly used dispersants octyl phenol ethoxylate (Triton X-100) and sodium dodecyl sulfate (SDS) were employed to explore the effects of single or mixed surfactants on the dispersion, sedimentation, and aggregation of multi-walled carbon nanotubes (MWCNTs). Nonionic surfactant TX100 showed much superior capability to anionic surfactant SDS in dispersing MWCNTs due to the benzene ring structure in its tail group. The addition of SDS reduced the adsorption of TX100 on the surface of MWCNTs and the consequent suspension of MWCNTs. The dispersing ability of TX100-SDS binary mixture was between those of individual SDS and TX100. The introduction of SDS greatly retarded the sedimentation and aggregation of suspended MWCNTs. The critical coagulation concentration (CCC) values of suspended MWCNTs dispersed by TX100 (2000 mg/L), SDS (2000 mg/L), and TX100-SDS (2000 mg/L of each component) were 48.6, 398, and 324 mM, respectively, for the Na+ treatments. The CCC values were much lower for Ca2+ treatments, which were 30.4 and 32.1 mM, respectively, for MWCNT dispersed by TX100 and TX100-SDS mixture. Overall, these results demonstrated that although the introduction of SDS did not improve the ability of TX100 in suspending MWCNTs, the suspensions exhibited more stable properties than those dispersed by TX100 alone. Our findings have important implications on the design of surfactant mixtures and the prediction on the behavior and fate of MWCNTs in water environment.