The right-back has signed a contract with David Moyes’ side until 2023, with the option of a further two years.
Capped eight times by his country, the 28-year-old joins his former Slavia and current national team-mate Tomas Soucek at the London Stadium.
“I’m very happy I am part of the West Ham family,” Coufal said. “I will do everything so that West Ham will be successful.
“I know about the interest West Ham had in me for a long time but now finally I am here and I am so happy.”
Moyes said the club had been tracking the player for some time.
“Vladimir fits the profile of the type of player we want to bring to the football club — hungry, ambitious and determined,” he said.
“He is a proven talent with Champions League and international experience, but we believe his best years are still ahead of him here at West Ham.”
