A novel differentially fed dual-band implantable antenna is proposed for the first time for a fully implantable neuro-microsystem. The antenna operates at two center frequencies of 433.9 MHz and 542.4 MHz, which are close to the 402-405 MHz medical implant communication services (MICS) band, to support sub-GHz wideband communication for high-data rate implantable neural recording application. The size of the antenna is 480.06 mm3 (27 mm × 14 mm × 1.27 mm). The simulated and measured bandwidths are 7.3% and 7.9% at the first resonant frequency, 5.4% and 6.4% at the second resonant frequency. The specific absorption rate (SAR) distribution induced by the implantable antenna inside a tissue-mimicking solution is evaluated. The performance of the communication link between the implanted antenna and external half-wavelength dual-band dipole is also examined.