On June 29, 1984 Archbishop Joseph Mercieca ordained Spiteri to the priesthood in St John's Co-Cathedral in Valletta. He joined the diplomatic service of the Holy See in 1988 and has served in Panama, Iraq, Mexico, Portugal, Greece and Venezuela. In 2009 Pope Benedict XVI appointed him as the Apostolic Nuncio to Sri Lanka and Titular Archbishop of Serta. He was consecrated by Cardinal Tarcisio Bertone the then Cardinal Secretary of State, and Co-consecrated by the Maltese archbishops Paul Cremona and Joseph Mercieca in St John's Co-Cathedral. He served in Sri Lanka until October 1, 2013 when he was transferred to the diplomatic see in Ivory Coast.