Gor Mahia sailed into the money bracket after knocking out South African side and 2017 losing finalist SuperSport United on Wednesday.
The Kenyan champions qualified to the last 16 despite going down 2-1 in the return leg held in Pretoria on Wednesday.
And Olunga, who won the Kenyan Premier League title with Gor Mahai in 2015 before leaving for Swedish side Djurgardens IF, took to social media to congratulate his former side.
“Congratulations @OfficialGMFC for your qualification to #CAFCC group stage,” Olunga tweeted.
The 2018 Caf Confederation Cup Group stages will kick-off on May 6 to August 29 in 2018.