The player will join the Italian side from German club Schalke with Juve tweeting photos and a video on Thursday of McKennie arriving at the Turin airport.
McKennie, 21, is expected to undergo a medical and be unveiled as a Juve player on Friday. The deal is reportedly an initial loan deal for one season with an option to permanently join afterward.
He will become the first American to sign for Juventus and the club's first signing this summer since Andrea Pirlo replaced Maurizio Sarri as manager earlier this month.
Sources told ESPN on Wednesday that Pirlo was a key figure in getting the deal over the line.
McKennie made 28 Bundesliga appearances for Schalke last season and scored three goals.