Effect of electromigration on interfacial reactions between electroless Ni-P (EL-Ni) and eutectic Sn-3.5% Ag solder has been investigated. Sandwich-type reaction couples, Cu/EL-Ni/Sn-3.5% Ag/EL-Ni/Cu, having two EL-Ni/Sn-3.5% Ag interfaces were prepared with the help of reflow process. During reflow, Ni 3 Sn 4 intermetallic formed at the EL-Ni/Sn-3.5% Ag interfaces with a dark thin Ni 3 P layer underneath it. The reaction couples were annealed at 160 and 180 o C for various durations with and without the passage of DC current of 1x10 3 A/cm 2 density. It was found that current does not affect the stoichiometry of the intermetallics formed at the EL-Ni/Sn-3.5% Ag interfaces. The same Ni 3 Sn 4 intermetallic formed in the samples annealed at both the temperatures with and without current. Formation of Kirkendall voids in the Ni 3 P layer showed that Ni diffuses from EL-Ni through the grain boundaries of Ni 3 P to form Ni 3 Sn 4 . It was observed that current retards the Ni 3 Sn 4 growth at both the anode and cathode side interfaces at 180 o C, while no significant retardation was observed at 160 o C. This effect of electromigration on the EL-Ni/Sn-3.5% Ag interfacial reactions was due to the presence of Ni 3 P layer in between EL-Ni and Ni 3 Sn 4 .