We used a cold atmospheric plasma device as an innovative drug delivery technique in HeLa cells. The focus of this paper is to evaluate key parameters to achieve an efficient cell membrane permeabilization. Propidium iodide (PI) and FITC-Dextran were used as permeabilization markers. Cellular uptake was assessed by fluorescence microscopy and flow cytometry. Effect of plasma electric field and inhibition of clathrin-mediated endocytosis on plasma-induced permeabilization were studied. Cell viability and reactive oxygen and nitrogen species produced were measured. PI positive cell percentage was the highest for 1000, 10 000, and 100 000 pulses for 100-s long treatments. We found that cellular uptake was more efficient after a 30-min incubation time at 37 °C. Unexpectedly, plasma-induced permeabilization appeared to be dependent on endocytosis and plasma electric field did not seem to be responsible for the uptake by itself. No significant toxicity was observed 24 h after plasma treatment up to 1000 pulses. Level of reactive species produced in the treated medium increased with the number of pulses and peaked using 10 000 pulses. Considering a balance between cell viability and drug uptake, best results were obtained for 100-s treatments for 1000 and 10 000 pulses. A combined effect between plasma electric field and plasma-induced chemistry seem to be necessary for drug delivery.