Mohsin made 117 runs off 106 balls hitting three sixes and eight fours. Saif Badar of Pakistan contributed 88 runs for his team.
Sandeep Lamichhane took three wickets, while Aarif Sheikh and Dipendra Singh Airee grabbed two wickets each.
Nepal had won the toss and elected to field first.
U-19 Asia Cup: Afghanistan Set target of 124 runs for Nepal