From 2006 until 2007, she served as the Accountant of the Acholi Bursary Program, a project of the Royal Netherlands Embassy.

In 2011, she successfully contested the parliamentary seat of Women's Representative for Tororo District under the National Resistance Movement political party ticket.

[3] Sarah Achieng Opendi was the elected Member of Parliament for Tororo District Women's Representative until 2016.

During the primaries of the ruling National Resistance Movement political party, in October 2015, Opendi lost 42,718 vs 44,444 to Jacinta Ayo.

[11] Ayo went to court and was able to prove that the returning officers altered the vote tally sheets at more than one polling station.

The High Court sitting at Mbale on 28 July 2016, ordered that Opendi be kicked out of Parliament and that fresh elections be held.