Costello was appointed as CEO of World Vision Australia on 24 November 2003. Having spent much of his career focussing on local and domestic issues, Costello said he relished the opportunity to focus on international issues. In his first full year in the role, Costello became the face of Australia's response to the Boxing Day Tsunami. Costello led fundraising efforts, and World Vision Australia raised over $118 million for relief and rehabilitation programs. During Costello's tenure, the organisation grew from funding 480 projects benefiting 10.4 million people, to more than 800 World Vision development projects benefiting close to 100 million people across the globe including in Australia.