The present work demonstrates that the simultaneous determination of epinephrine (EPI) and acetaminophen (ACT) can be performed using a glassy carbon electrode (GCE) modified with a novel multi-walled carbon nanotubes (MWCNTs), nickel hydroxide nanoparticles (NHNPs) and Mg–Al layered double hydroxide (LDH) composite (MWCNTs–NHNPs–LDH/GCE). The electro-oxidations of EPI and ACT were investigated using cyclic voltammetry (CV), differential pulse voltammetry (DPV) and chronoamperometry (CA) methods. Under optimum conditions, DPV indicated linear relationships between oxidation peak current and EPI and ACT concentrations in the ranges of 0.04–60 mM and 0.02–40 mM with detection limits of 11 and 5 nM, respectively. The proposed method was successfully applied to the determination of these compounds in human urine and blood serum samples.