Erythromycin A (EA) is now one of antibiotics limited in seafood products in general and in giant freshwater prawns (Macrobrachium rosenbergii) and tilapia (Oreochromis niloticus) in particular while exporting to the US, EU, Japan, Canada. There are many methods used for analyzing this antibiotic in these aquatic species (e.g., ELISA, HPLC, LC-MS/MS, GC-MS). A new, sensitive, analytical approach for determination of erythromycin A using stripping square wave voltammetry at the slowly dropping mercury electrode was developed and validated to quantify this antibiotic with simple and short time analysis; the method is inexpensive and performs best at moderate concentrations of erythromycin A. Electrochemical signals were measured at potential wave -1430 mV. The optimal experimental parameters for the method were: supporting electrolyte ammonium acetate 0.1 M, pH 8.0, the solvents for dissolving erythromycin standard: acetonitril, Vstart = -400 mV, Vstop = -1700 mV, Vstep = 6 mV, Vpulse = 40 mV, Tdrop = 5000 ms , Velctrolise = -1100 mV, Telectrolise= 5 s. The method showed high recovery (85.07 ÷ 96.50%), high sensitivity (lower limit of detection, LoD = 0.57 µg.kg-1 in giant prawn and LoD = 0.52 µg.kg-1 in tilapia) and high precision (RSD 0.91 ÷ 2.1%) as well as excellent linearity (r2adjusted ≥ 0.99999).