Mercer became an Israeli citizen, and served in the Israeli Defense Forces for two years. Mercer also played for the Israeli national basketball team in the 1986 FIBA World Championship and 1987 Eurobasket Championship. In 1982, having formerly been Baptist, he converted to Judaism. He said that "I guess you could call me a Messianic Jew or a Christian Jew. When I was over there it was the closest I felt to God. I really defend the state of Israel..." In 2006 he was honored by the Israeli Consulate to the Southeast United States and made an official goodwill ambassador for the State of Israel.