•Controllable and easy to scale up design of innovative composites (from inexpensive coconut shell-derived activated carbon and treated MWCNTs) with improved physico-chemical properties.•The composites exhibit superior capacitance value (90.2 F/g), salt adsorption capacity (SAC) of 14.1 mg/g at 1.0 V and stability (95.7% after 100 cycles at 1.0/0 V).•The composite can be a promising candidate for large scale CDI electrode applications. Aiming at more efficient use of coconut resources to achieve multi-purpose goals, this work proposes an innovative composite for capacitive deionization (CDI) electrode in desalination applications when using coconut shell-derived activated Carbon (AC) as a matrix into which a certain amount of carbon nanotubes (CNTs) is incorporated. The electrochemical studies show that the optimized 9mAC:1CNTs electrode with a surface area of 630 m2/g has a specific capacitance of 90.2 F/g (at scan rate of 20 mV/s), salt adsorption capacity (SAC) of 14.1 mg/g at 1.0 V. SAC value is retained as high as 95.7% after 100 adsorption–desorption cycles at 1.0/0 V, showing a good cyclic stability of the electrode composites. Moreover, a calculated specific energy consumption (SEC) value of 0.312 kW h/m3 was quite low compared with other CDI electrodes reported in literature. Briefly, the present study indicates that AC-CNTs composite can serve as promising CDI electrode materials for desalination application.