The 26-year-old shot-stopper is currently with his country preparing for their friendly with the Republic of Ireland on Wednesday and the paperwork for a one-month loan to Huish Park is expected to be completed on Thursday.
The Glovers wasted no time in finding a replacement for injured number one Marek Stech who broke his finger in the 1-0 loss to Birmingham on Saturday, and regular first-team football back in the Championship will help Hennessey as he looks to return to his best after 16 months on the sidelines.
Hennessey, now fit again after twice damaging his cruciate knee ligaments, has not played in a senior fixture since initially sustaining the injury in April 2012 despite having played in a number of Wanderers' pre-season fixtures recently.
"After 18 months out, I am pleased that Wayne has been given the opportunity to go and play some first-team football," head coach Kenny Jackett told the club's official website.
"He has done all of the training sessions and has played in some of the pre-season fixtures but needs a regular run of games.
"It will be a good chance for Wayne to build up his match fitness, and is also in the best interests of the club to see him enjoy some regular first-team action."