[1] Okello previously featured for Samia AllStars before joining Kenyan Premier League side Chemelil Sugar F.C.
[2] He later left for lower-tier side Vihiga Bullets, then arrived at Nzoia Sugar F.C.
In Aug 2022, Okello made a switch to Kakamega Homeboyz F.C.
[6][7] Okello later joined Nairobi City Stars,[8] on loan, in the March 2023 transfer window for the rest of the season.
He earned his debut on 5 April 2023 as a second-half substitute against KCB in Kasarani Annex.