On 30 June 2010, Mulder agreed to join Bulgarian side Levski Sofia. On the following day he made his unofficial debut in a friendly against Metalist Kharkiv, before signing a two-year contract on 2 July as a free agent. He made his competitive debut on 22 July in a 2–0 away win over Dundalk in the second qualifying round of the 2010–11 UEFA Europa League.
