Lepani plays as a forward for Panamex FC; he has represented Papua New Guinea national football team at international level on 12 occasions.
Born in Papua New Guinea in January 1982, Lepani moved to Hawaii as a young child, due to his father, a diplomat, being posted there for work.
Further work and university commitments stalled Lepani's club career until the 2007–08 season, when he joined Ku-ring-gai district side Lindfield FC.
Lepani made his debut for Gigira Laitepo on the opening day of the 2011–12 season, in a 3–0 loss to PRK Hekari United in November 2011.
[14] On 16 June, the midfielder played in Edge Hill's 6–1 loss to Stratford Dolpins; Lepani was substituted after his team had the first of two players sent-off.
These eight caps remained Lepani's only appearances for the national team until he was called up for the men's football tournament at the 2011 Pacific Games in New Caledonia.
[21] He justified his inclusion in the squad by scoring Papua New Guinea's fourth goal in their 4–0 win over the Cook Islands on 27 August 2011, after coming off the bench.
[28] Lepani later admitted he was "extremely" disappointed not to have made the squad, and revealed that a gash to his knee, which required "7 stitches and one week out from training camp" contributed to his exclusion.
[34] Nathaniel's brother, Andrew Lepani, is also a footballer and has played for Papua New Guinea, Cosmos Port Moresby and PRK Hekari United.
[38] In November 2006, Nathaniel met World Cup winner Christian Karembeu at the launch of the Oceania Football Confederation's OFC Champions League 2007.