The 29-year-old is the 10th new arrival at The Hawthorns in what has been a busy summer for the Premier League club.
Albion have also signed Brown Ideye, Sebastien Pocognoli, Jason Davidson, Joleon Lescott, Georgios Samaras, Cristian Gamboa, Chris Baird, Craig Gardner and Andre Wisdom.
Varela, who has been capped 26 times for Portugal, can play on either wing, and will give Albion boss Alan Irvine options in attack.
“Silvestre is a vastly-experienced player, both with Porto and his national team, and I’m delighted we’ve managed to secure his services,” Irvine said.
“He’s got pace and power, gets his fair share of goals and is also a creator of chances for others.“He’s a fantastic addition to our squad.”
Well, the snobs are out in force. Look at a club that doesn't have a ground like an airport and 'global following' and the armchair Napoleons, internet-glaring Billy-no-mates that probably take up crap jobs and need to follow a big club to fill a hole in their dull lives because they fail to do that themselves, get out the pasties, sit their fat arses down and give it some. Don't bother Albion fans, let the shirt-wearing chimps throw their faeces - gathered from plump, complacent success-pampered bums - and be done with it. Strange how such a sport that's meant to please the common man has turned some of them into the Duke of Edinburgh, fast-bellied nothings who think they own the game because they put on a Man Utd shirt or any shirt of a top club. Well, you're not. Success hasn't enhanced your slack-jawed, bumpkin character, it's just made it worse, a sneering, pseudo-superior village idiot, but because he's got an OT season ticket has gotten it into his/her/it's head that the world is his/hers/its. Football's a game, not a religion and if you think that following a big club has reflected its glory and prestige onto your shabby, Cro-Magnon soul ('YEH, I FOLO MANU YOU LITTL CLUB BASTSARDS, LOL, LMAO!') then I'd reconsider your viewpoint drastically, because those beams of greatness are bouncing off you into the ether effortlessly. I'm getting to dislike the good and reasonable fans of top clubs because they don't seem to pipe up as loud or as gratingly as their low-rent breathren, leaving the more Worzel-Gummidge-souled maggots to nick all their airspace and use it for themselves in all its simple, toxic, text-speak-thinking glory. I'd invite those more intelligent types to come along and utilise it quickly before their entitled, doorstep-browed slimy mates use it all up. Yep, that was a rant, and I quite enjoyed it, thanks.- IanJames