The pair worked together at Wolves and are now back together at London stadium.
The defender told the club's website: "I’m so delighted to be here and to join such a massive Club, so I just can’t wait to get started and get going.
“I just got a call from my agent, and he said that West Ham were interested, and as I’ve said West Ham are a massive Club and I wanted to hear more about it. I’m so glad that it finally got done and that I am here now.
“I had some really good conversations with both of them (Julen Lopetegui and Tim Steidten). I spoke to the manager a lot and he said about making such a big noise, and that he wants to be more attacking, really try to progress and get this Club in a better position. The Club has done so well in recent years, so we want to keep up that form and grow as much as possible.
“I think it's just his ethos as a coach. He’s implemented his targets, how he wants to be from the start and I think everyone, once they get to know him, will know this is what he’s about. You need to make sure you abide by the rules and make sure you do your best every day. I think he sets such high standards where you have to be on it every day in training and I’m sure that will translate to games.
“He wasn’t with me for such a long time (at Wolves) but I loved every minute working under him. He helped me so much with my career and gave me much more responsibility, so he’s definitely someone that wants to improve players and make sure everyone gets to the top of their game. You will see that the standards in training will rise and everyone wants to perform at the highest level under him.
“I can’t wait because he has had such a good managerial career at the clubs he has been at before and done such a good job at Wolves. I’m delighted to be a part of his team and will be doing the best that I can."