Walsh, who has been Bangladesh's bowling coach since 2016, takes over as interim coach from former Zimbabwean cricketer Richard Halsall.
The position of Bangladesh' head coach had been vacant since October, when Chandika Hathurusingha quit after three years at the helm.
Meanwhile, Khaled Mahmud will no longer be a part of the support staff.
"Since I will be going to Sri Lanka, a lot of the directors also will come with me. I personally feel that [Khaled Mahmud] Sujon should go as team manager," ESPNcricinfo quoted Bangladesh Cricket Board (BCB) president Nazmul Hassan as saying.
"We still haven't talked to him about it. We have finalised on the other roles like we have also decided to give the batting duties to someone which we will announce on Tuesday," he added.
Bangladesh named a 16-man squad for next month's tri-nation T20I series involving Sri Lanka and India.
The squad is as follows:
Squad: Shakib Al Hasan (c), Mahmudullah Riyad (vc), Tamim Iqbal, Soumya Sarkar, Imrul Kayes, Mushfiqur Rahim, Sabbir Rahman,
Mustafizur Rahman, Rubel Hossain, Taskin Ahmed, Abu Hider, Abu Jayed, Ariful Haque, Nazmul Islam, Nurul Hasan, Mehedi Hasan. (ANI)