Background: Congenital absence of the lumbosacral facet joint is extremely rare, with only 26 cases reported in the literature. Here, we present a patient with the unilateral absence of the left fifth lumbar inferior articular process and reviewed the relevant literature. Case Description: A 32-year-old gentleman, who had undergone right L4-5 lumbar microdiscectomy 3 months ago now presented with acute low back and left leg pain following a fall. He is now presented with acute low back and left leg pain following a fall. Plain radiographs of the L-S spine revealed an absent left L5–S1 zygapophyseal joint. The magnetic resonance imaging and computed tomography studies additionally confirmed an absent unilateral left L5 lumbar inferior articular process. Conclusion: Patients presenting for lumbar surgery may have unilaterally absent lumbosacral zygapophyseal joints, which may impact the outcome of surgical treatment.