The Nigeria international signed a five-year deal with the club on the eve of the finals in Russia where Nigeria will play their opening group game against Croatia on Saturday.
An Olympic bronze medallist, Etebo expressed his gratitude to Feirense for their backing during his two-year stint in Portugal, although he had been on loan at Las Palmas for the past six months.
He said: “I’m very excited about the move; hopefully, I will help the club return to the Premier League. But for now, the World Cup is my main focus.
“I also want to thank CD Feirense for all their support and love given to me in my two years’ stay in Portugal. I will forever support the club as they will remain in my heart.”
The 14-cap international will hope to get some action during the World Cup after impressing as a substitute in the Super Eagles’ recent 2-1 defeat to England at Wembley.