In this study, we have developed an implantable electronics unit (IEU) for driving an undulation pump–left ventricular assist device (UP–LVAD). The IEU consists of a pump driver, three series-connected lithium ion batteries (1800 mAh), a charger, and a transcutaneous information transmission system. These electronic subunits were encapsulated in a case (110 × ∼80 × ∼30 mm) made of epoxy resin. The IEU was evaluated in two animal experiments using goats implanted with the UP–LVAD. The lithium ion batteries in the IEU provided 30-min energy supply daily to the UP–LVAD. The transcutaneous information transmission system transmitted data bidirectionally between the IEU and the personal computer at the data transmission ratio of 56 kbps without any transmission error. We could obtain survival days of 27 and 28 days supporting cardiac function with the UP–LVAD system. The temperature inside the IEU case was maintained under 45°C, and there was evidence of a burn on the surrounding tissue in autopsies in each experiment. Based on the results, the IEU is promising to be suitable for drive and control of an implantable UP–LVAD.