The Estlink 2 electricity link between Finland and Estonia was operational again on Friday, according to Finnish transmission system operator Fingrid.
The link returned to commercial use on Friday after nearly six months out of service. The repair work has been carried out at sea since May.
The subsea cable was damaged on Christmas Day. The oil tanker Eagle S, reportedly part of Russia's shadow fleet, is suspected of causing the incident.
Although the damage to the transmission link did not impact the stability of Finland's electricity system, it temporarily reduced the transmission capacity between Finland and Estonia by 650 megawatts.
Last week, the National Bureau of Investigation (NBI) announced that three Eagle S officers are suspected of involvement in the cable damage incident.
Investigators said the Eagle S damaged its anchor chain by dragging one electrical cable and several data cables on Christmas Day.
