We described two cases and the techniques for using the ultrasound (US) to guide lumbar intradiscal injection with platelet-rich plasma (PRP). The two cases suffered from chronic low back pain. Magnetic resonance imaging revealed posterior annular tear of the L5/S1 intervertebral disc (IVD) in the first case and L4/5 and L5/S1 IVDs in the second case. For the US-guided lumbar intradiscal injection, the patient was placed in a prone position. By placing the transducer in the axial plane at the interlaminar space, the needle was directed toward the center of the aimed IVD. The needle tip was ensured inside the IVD by using the end-feel of sudden reduction of resistance and the poking technique with the transducer oriented in the paramedian sagittal oblique plane. At the follow-up, both patients had significant improvement after the intradiscal PRP injections (visual analogue scale from 7.5 to 1.5 on average). The report indicated US-guided lumbar intradiscal PRP injection to be a feasible approach for treatments of low back pain. Familiarization of the anatomy and sonoanatomy of the lumbar spine is fundamental to achieve the success of intradiscal injection.