The 28-year-old right-back has joined the Baggies on a four-year deal for an undisclosed fee.
Cameroon international Nyom joined Watford last summer but has quickly moved on and is looking forward to starting afresh with Albion.
"I received a call from my agent last night and he told me about the offer to come here and I was happy to do so," he told the club's official website.
"Last year was my first in England. I was so happy to play in the Premier League as I think it is one of the best leagues in the world. I enjoyed it a lot.
"The Premier League is completely different to other Leagues because here there is more intensity, more fight... the atmosphere in England is better than Spain.
"The team here is good and with good players, a team that plays together. I'm going to try to bring energy and to give my best every game; I want to help the team."