Jamshed, 23, struggled in the twin series against South Africa in the UAE and then in South Africa, scoring 18 and 19 in the last two Twenty20 matches.
He was replaced by Sharjeel, another 24-year old left-hander who has yet to represent Pakistan.
Also left out are Shoaib Malik, Abdul Razzaq and Abdur Rehman.
Malik and Razzaq were part of Pakistan's squad to South Africa but were sent back after suffering injuries.
Pakistan drew the two-match T20 series 1-1 but won the three-match one-day series 2-1, their first series win in South Africa.
Mohammad Hafeez will lead the T20 squad.
Paceman Mohammad Irfan was ruled out due to injury.
Pakistan play Afghanistan in a T20 game on Sunday in Sharjah -- the first-ever T20 between the two nations. Pakistan then play Sri Lanka in two T20s on December 11 and 13 in Dubai.
Pakistan and Sri Lanka will also play five one-day and three Tests in UAE, for which squads will be named later.
T20 squad: Mohammad Hafeez (captain), Ahmed Shehzad, Sharjeel Khan, Sohaib Maqsood, Umar Amin, Umar Akmal, Shahid Afridi, Zulfiqar Baber, Bilawal Bhatti, Junaid Khan, Sohail Tanvir, Anwar Ali, Saeed Ajmal, Harris Sohail.