Sam Allardyce's side moved up to sixth in the Premier League with the 1-0 success at St James' Park and Diame is encouraged by the Hammers' recent form.
"It was a fantastic result against Newcastle, probably the best since I joined the club, and we worked very hard for the three points," he told the club's official website.
"The manager gave me a lot of confidence going into the game so I tried to give it back on the pitch and I think I did a good job."
Diame, a free transfer signing from Wigan in the summer, added: "When I spoke to the club I knew they were trying to build a very good team. We are working very hard every day on the training ground and you can see it is paying off.
"People did say 'Why are you going to West Ham when you can play in the Champions League?' but they can see why I did now.
"It is a very big club in England and I am very happy to be here, now I am hoping that our good performances will continue."