Okello has previously played for KCCA, BUL, SC Villa and Vipers in the StarTimes Uganda Premier League.
The striker has joined the Kenya Police as a free agent after parting ways with Iranian topflight side Paykan FC at the end of last season.
The midfielder has joined on a one-year contract that will see him play for the club until the end of the season.
The 27-year-old South Sudanese international reunites with his national teammate Rashid Toha who crossed over from Arua Hill.
Okello returns to Nairobi after a year, having played for Kenyan champions Gor Mahia for two seasons from 2020-2022.
He scored eighteen goals in about 47 appearances for the green army.
He started his club career at SC Villa young in 2012 but was later sent to BUL, where he played until the end of the 2013/14 season.
From there, Okello played for African Lyon and Mbeya City in Tanzania between 2014 and 2017 before returning to KCCA FC in the 2017/18 season and then Vipers from 2018 to 2020.
08:33 - 20.08.2023
Defending champions Vipers, KCCA FC and NEC have been cleared to host StarTimes Uganda Premier League matches at night under floodlights.
04:22 - 17.08.2023
Earlier in the week, the coach summoned 33 players who will start preparations for the 2023 Africa Cup of Nations qualifier against Niger on September 7th in Marrakech.
17:19 - 14.08.2023
BUL FC will play the winner between KCCA and URA FC, who clash over the weekend, in the final of the FUFA Super 8 cup.