Lemanis has been in charge of the Breakers for the past eight seasons, taking them from near the bottom of the competition to three-time champions and he will reportedly be unveiled as Boomers' coach soon.
The Breakers have called a media conference for tomorrow morning, when the makeup of their coaching team will be announced.
Assistant coach Dean Vickerman is likely to take over, with support from Judd Flavell. Paul Henare and Pero Cameron could come into the frame as a second assistant.
Lemanis was seen as a favourite for the Australia job along with Perth coach Rob Beveridge.
Basketball Australia was prepared for Lemanis to work part-time and to continue to coach an ANBL club but Lemanis didn't think he could do justice to both jobs and preferred a full-time appointment.
