Lachman, 25, has signed a two-year contract after joining from Dutch side FC Twente for an undisclosed fee.
“I’ve always dreamed of playing in England so I’m really looking forward to playing for Sheffield Wednesday and in the Championship,” Lachman, a Curacao international, told the Owls’ official website.
“The Championship excites me and the plans of the club going up higher makes me excited. I’ve always played in Holland and I want to try something different.
“Playing in a stadium like Hillsborough is new for me, you don’t see many stadiums like this in Holland.”
Lachman progressed through Ajax’s youth system and had spells at FC Groningen and Zwolle before joining FC Twente last year.
He added: “I’m a player that likes to play football, I like to take risks. I’m a confident player.
“I am not the kind of player who kicks the ball into the stand, I like to keep the ball at my feet and play the game.
“I want to show that I am good enough to be a first choice and I am ready, waiting and excited to get started.”