The Senegalese took an early lead in Ndola as Aliou Badji struck after 12 minutes.
In first-half stoppage time, Ibrahima Niana had the chance to double Senegal's lead but his penalty was saved by Moussa Camara.
Senegal have reached the final for the second tournament running.
They contested the final for the first time in 2015 but were beaten by Nigeria.
Neither Senegal nor Zambia, who beat South Africa 1-0 on Wednesday, in have ever won the tournament before.
Sunday's final will be played at the Heroes National Stadium in the capital Lusaka.
Senegal will meet hosts Zambia in Sunday's final of the Under-20 Africa Cup of Nations after beating Guinea 1-0 in Thursday's semi-final.