Meier, 37, scored just one goal in 12 games for the Wanderers before a mutual termination of his contract was confirmed on Friday.
The former Eintracht Frankfurt striker - fondly nicknamed Fussballgott, or 'God of Football', by the Bundesliga club's fans, struggled with the pace of the A-League and will return to Germany for "personal reasons".
"I am thankful for this experience," Meier said via a statement. "The Wanderers are a top professional football club, everybody was very helpful and supportive, the supporters were great and I really enjoyed my time here.
"I will miss my team-mates, the club and the fans and wish them all the best in the rest of the season."
Western Sydney announced the signing of former West Brom and Nottingham Forest striker Simon Cox on Thursday.
The Wanderers are eighth in the A-League table and host Perth Glory on Sunday.