Cystic renal diseases are characterized by intrarenal cysts of different size and number. Further important diagnostic criteria include, e.g., liver fibrosis. The latter represents a significant cause of morbidity and mortality in autosomal-recessive polycystic kidney disease (ARPKD), whereas patients with autosomal-dominant polycystic kidney disease (ADPKD) can develop hepatic cysts without fibrosis. We report the use of transient elastography [FibroScan®, (FS)] for early and noninvasive detection of increased liver stiffness as marker of liver fibrosis. Compared with matched healthy controls, ADPKD patients (n = 7) showed no significant difference in liver stiffness (5.3 kPa vs. 4.5 kPa; ns). ARPKD patients (n = 7) had significantly increased median liver stiffness compared with controls (12.0 kPa vs. 4.5 kPa, p = 0.002) and ADPKD patients (12.0 kPa vs. 5.3 kPa, p = 0.002). Conventional ultrasound revealed evidence of liver fibrosis in only four of seven ARPKD patients (57%) compared with 100% detection by FS. Additional laboratory examinations showed no pathologic liver parameters. In conclusion, our data found FS to be a valuable, sensitive, and noninvasive new tool for early evaluation of liver fibrosis in cystic kidney diseases. This could facilitate diagnosis, monitoring, and management of liver involvement in ARPKD or any other cystic kidney disease.