Smith and Babar stitched a dominant 141-run partnership for the opening wicket.
Babar Azam and Steve Smith also suffered in fielding due to miscommunication.
Jadeja took 44 deliveries to score 27 runs while batting at No. 6.
Iyer added for the first three T20Is only, as replacement for injured Tilak Varma.
Babar was left frustrated after Smith denied him a single.
The moment unfolded during the 47th over of Pakistan's chase.