The high consumption of watermelon (Citrullus lanatus) in Senegal has raised questions about the quality of this fruit and its health consequences. Watermelon bought from three different localities in the Dakar peninsula (Rufisque, Castors, and Tilène) were studied. Their nitrates, chlorides, and fluorides ions contents were assayed by specific electrodes, while the analyses of sodium ions were done by flame photometry. Nitrates concentrations were found to be about 210 mg/l, 250 mg/l, and 170 mg/l respectively for samples from Rufisque, Castors, and Tilène. Analyses of fluorides showed concentrations of 6 mg/l, 8 mg/l, and 7 mg/l respectively for the samples from Rufisque, Castors, and Tilène. The results for chlorides revealed concentrations of 100 mg/l, 40 mg/l, and 120 mg/l respectively for samples from the same three localities. And finally, sodium concentrations obtained were roughly similar for all three localities, and were respectively 27 mg/l, 26 mg/l, and 26 mg/l.