Graphene nanoplatelets are a novel class of carbon nanostructures. They possess an ultra high surface area, and thus have great potentials for the use as sorbent materials. We herein demonstrate the use of graphene nanoplatelets as an adsorbent material for solid-phase extraction. Surface compositions of graphene nanoplatelets were examined by X-ray photoelectron spectroscopy. Scanning electron and transmission electron microscopies were performed to elucidate the morphology of graphene nanoplatelets. Three chlorophenols, 3-chlorophenol, 4-chlorophenol, and 2,4-dichlorophenols were selected as model analytes and extracted on a graphene nanoplatelets-packed solid-phase extraction cartridge, followed by elution with alkaline methanol. The extracted chlorophenols were identified and quantified by UV-vis spectrophotometer. Under the optimized experimental conditions, good linearity ($R^2$ >0.9969), recovery (95-103%), precision (<12%), and accuracy (< ${pm}9$%) were achieved. The advantages of graphene nanoplatelets as solid phase extraction adsorbent, such as good reusability and no impact of sorbent drying, have been detailed. The present study proposes a useful method for water sample pretreatment and reveals the potential of graphene nanoplatelets as an excellent sorbent material in analytical processes.