Born in Libera, Siafa Dempster migrated to the United States where he joined the Philadelphia Lone Star FC Academy. He played DII college soccer for two years at Holy Family University where he made 14 appearances for the Tigers before transferring to Bryn Athyn College where he served as captain and made 33 appearances (31 starts), had 11 goals and three assists for the Lions.

At the senior level, Dempster has played for FK Tomori in Albania and Michigan Stars FC of NISA before rejoining the Stars last Fall.