"Thiago Silva has told me a lot about the club and its facilities, and it will be nice to have him as my teammate," Lucas told reporters.
"However, I have to admit that I do have a bit of fear about how things will pan out. I don't know how well it will go.
"I am not thinking about money, but I am more concerned with whether my next destination will be the right one. PSG's ambition and the presence of the other Brazilians convinced me."
Lucas had been targeted by a host of top European clubs in the summer.