The NASA flag bearer had also supported Liverpool and Bayern Munich in the past.
Speaking in an interview with Radio Maisha on Tuesday, the former Prime Minister counted a number of clubs he has supported before landing on the Arsene Wenger managed outfit.
Rivals Manchester United were his favourites in the 1970's but he says he stopped supporting them due to violence.
“For a whole year, Manchester United was playing without fans in the stadium. That is when I moved to support Arsenal. Since that time, I never left Arsenal.”
The ODM leader, who usually use football language in his political rallies, has previously supported Liverpool, Hannover 96 and Bayern Munich; the latter two being during his studying period in Germany.
He also played for Luo Union football club (later known as Re-Union FC) in the 1960’s.