This work describes a sequential injection analysis (SIA) method for on-line strippping voltammetric determination of Pb(II), Cd(II) and Zn(II) using an injection-moulded electrochemical fluidic chip consisting of 3 conductive carbon fiber-loaded polymer electrodes embedded in a plastic fluidic holder. The sample containing the target metals and a solution containing Bi(III) were aspirated in the holding coil of the SIA manifold. Then, the flow was reversed and the two solutions were directed to the fluidic cell through a mixing coil which induced mixing of the two zones. Upon reaching the cell, simultaneous reduction of the target metals and Bi(III) occurred resulting in the formation of a metal-Bi alloy on the working electrode. Finally, the accumulated metals were stripped off the bismuth-film electrode via a positive potential scan and the oxidation current was recorded. The experimental variables (concentration of the bismuth plating solution, deposition potential, sample volume, stripping mode) were investigated and the potential interferences were assessed. The limits of quantification were 2.8 μg L−1 for Pb(II), 3.6 μg L−1 for Cd(II) and 4.2 μg L−1 for Zn(II) and the the within-chip and between-chip % relative standard deviations were ≤6.3 % and ≤14 %, respectively. Finally, the sensor was applied to the determination of trace metals in a fish food sample.