Krychowiak made his debut for the club in a 3–1 loss against Brighton & Hove Albion on 9 September 2017. Three weeks later, on 30 September 2017 against Watford, he set up West Bromwich Albion's first goal of the game, in a 2–2 draw. Since joining the club, Krychowiak became a first team regular for the side, playing in the midfield position. By November, he found himself placed on the substitute bench, with Jake Livermore and Sam Field preferred ahead of him. This led to reports over Krychowiak's future at the club, but new manager Alan Pardew wanted to keep him. As the season went by, he found himself alternating between the substitute bench and the starting eleven role. Krychowiak found himself in a controversy when he refused to shake Pardew's hand after being substituted in the 59th minutes during a 4–1 loss against Leicester City on 10 March 2018. After the match, Krychowiak was criticised by Pardew for his actions and was fined as a result. This resulted in him being dropped to the substitute bench until Pardew's sacking. Following the appointment of Darren Moore, Krychowiak played the remaining matches of the season, as the club were relegated to the Championship. At the end of the 2017–18 season, Krychowiak made 31 appearances in all competitions. Following this, he returned to Paris Saint-Germain.