Atem was born in Bor, South Sudan.[1] He and his family spent four years in the Kakuma refugee camp in Kenya before moving to Sydney, Australia, where he was introduced to basketball by his high school teacher. He started to take the sport seriously when he was offered a scholarship to Illawarra Sports High SchoolinWollongong, and from there he earned a scholarship to Northern Oklahoma College in the United States.[2] Atem was on the 2012–13 roster at North Oklahoma College, but he was forced to redshirt the season, which made him re-think his commitment and ultimately led to him deciding not to return to the program for the 2013–14 season.[3]
Atem made his Australian state league debut in 2014, playing a handful of games for the Ipswich Force in the Queensland Basketball League (QBL). He spent the majority of the year with the Force's Southern Basketball League (SBL) affiliate team and was named the MVP of the SBL team.[4][5]
In November 2015, Atem signed with the North-West Tasmania Thunder for the 2016 SEABL season.[7] In 20 games for the Thunder, he averaged 2.5 points and 1.3 rebounds per game.[8]
In December 2017, Atem signed with the North Adelaide Rockets for the 2018 season, returning to the Premier League for a second stint.[12] In 18 games, he averaged 13.2 points, 7.4 rebounds and 1.0 assists per game.[13]
In March 2019, Atem signed with the Shepparton Gators of the Big V Division One.[14][15] In 27 games, he averaged 19.37 points, 9.89 rebounds and 1.11 assists per game.[16]
In 2020, Atem played for the South West Metro Pirates in the Queensland State League (QSL).[17]
In March 2021, Atem signed with the Northside Wizards for the 2021 NBL1 North season.[18][19] In 12 games, he averaged 13.33 points, 6.0 rebounds and 1.41 assists per game.[20]
In April 2022, Atem re-signed with the Wizards for the 2022 season.[21] In 15 games, he averaged 4.6 points and 2.5 rebounds per game.[22]
Atem joined the Ipswich Force for the 2023 NBL1 North season. In nine games, he averaged 6.11 points and 3.78 rebounds per game.[23]
