The lanky player underwent trials with Celtic last month. Mothatego plays for Botswana Premier League side (BPL) Gaborone United, and managed to impress coach Ernst Middendorp's technical team.
"Yes, it is true. The deal will be finalized soon. Mothatego did well to impress the technical team," Mitchell told Goal.
Mothatego was part of the United team that lost 2-0 to SuperSport United on Saturday in a Caf Confederation Cup preliminary match. The 26-year-old will join two other Botswana internationals, midfielder Mogogi Gabonamong and winger Joel Mogorosi at Celtic in July, once the deal is finalized.
Meanwhile, player agent Mitchell also dismissed rumours linking Bafana Bafana defender Buhle Mkhwanazi with SuperSport United and Orlando Pirates.
"It is not true. Both teams haven't contacted me regarding their interest in the player," Mitchell said.
The University of Pretoria vice-captain has done very well since joining Amatuks on a permanent deal from Mamelodi Sundowns. The 23-yea-old defender was part of the Bafana Bafana squad at the 2014 Chan tournament and he played one match for the national team.