On 8 August 2011, Bücker was announced as Lebanon's new head coach, with the former national team manager taking over the reins ten years after leaving the position. He is the first ever coach to bring Lebanon to the fourth and final qualifying round of the world cup. During this period, the Lebanese national team made impressive results. They defeated United Arab Emirates 3–1 in Beirut, South Korea 2–1 in Beirut, and Kuwait 1–0 in Kuwait in the third round. For the first time in their history, Lebanon defeated Iran by a single goal on matchday 4 of the final round. Bücker announced his retirement in May 2013, effective from 11 June 2013, after match that his side defeated by Iran 4–0.
Bücker considers himself as "half-Lebanese" and is married to a Lebanese woman. He has been a resident of Beirut for many years, expressing his love for his adopted nation.
In 2012, former Lebanon national team member Buddy Farah stated that the credit for Lebanon's success and improvement should go to Bücker and that he was the best thing ever to happen to Lebanese football.