Multi-walled carbon nanotubes (MWCNT) have been widely studied for adsorption of pharmaceuticals and personal care products (PPCP). However, effluent organic matter (EfOM) is found to compete with PPCP for sorption sites on MWCNT, thereby markedly reducing the adsorptive capacities of MWCNT for PPCP in wastewater effluent. Herein, we report that precoagulation of secondary wastewater effluent effectively mitigated the competitive adsorption of EfOM and increased the adsorption capacities of MWCNT for acetaminophen, caffeine, triclosan, and carbendazim by up to 34%. Analyses of the coagulated waters using size exclusion chromatography and three-dimensional fluorescence spectrophotometry revealed that precoagulation primarily removed biopolymers and humic substances; the latter is known to suppress PPCP adsorption onto MWCNT. Moreover, the removal of EfOM by precoagulation reduced membrane permeability decrement and relieved membrane fouling. These results suggest that coagulation, a conventional technique widely used by water treatment plants, is a viable pretreatment approach for filtration of PPCP in wastewater by MWCNT. This finding also demonstrates the potential of integrating conventional technology and novel nanotechnology for cost-effective, advanced wastewater treatment.