Bilago passed away at the Muhimbili National Hospital (MNH) in Dar es Salaam yesterday where he was admitted earlier this week for medical treatment.
The MP was flown from Dodoma on Tuesday this week where he was attending the ongoing parliament session and rushed to MNH after suffering abdominal pain.
"I am sorry to have to inform you that our friend, brother and colleague, Kasuku Bilago, has just passed on. I am at his deathbed and will update you as soon as possible," CHADEMA national chairman Freeman Mbowe said in a brief statement yesterday.
CHADEMA did not immediately disclose the cause of death.
Bilago previously worked as a teacher for public schools under the Ministry of Education and later rose to become a regional Tanzania Teachers' Union (TTU) leader.
He initially joined the ruling Chama Cha Mapinduzi (CCM), but later jumped ship to CHADEMA and won election in 2015 as an opposition MP.
Bilago graduated with a diploma in education from the Monduli Teachers' College in 1990 and worked as a teacher for six years before joining the Tanzania Teachers' Union and ultimately becoming a lawmaker.
The late legislator went for further studies in the United Kingdom and received a bachelor of philosophy degree in education management (BPhil) from the Newcastle University in 2006, before attaining a masters' degree in international relations from the Commonwealth Open University (UK) in 2007.