Warm ischemia (WI) and bleeding during laparoscopic partial nephrectomy (LPN) place technical constraints on surgeons. Our aim was to develop a safe and effective laser-assisted LPN-technique without the need for WI. In this study, a diode laser-emitting light at a wavelength of 1,318 nm at output powers between 45 and 70 W in continuous-wave mode was used. Light was coupled into a flexible 600-μm bare fiber to be transported to the tissues. After dry lab experience, 13 patients (six males, seven females) underwent five open and eight laparoscopic/retroperitoneoscopic partial nephrectomies. Postoperative renal function and serum C-reactive protein (CRP) were monitored and coagulation depth and effects on resection margins (RR) were evaluated. Demographic, clinical, and follow-up data are presented. Mean operative time was 116.5 min (range 60-175 min) with mean blood loss of 238 ml (range 50-600 ml). Laser light application took a maximum of 17 min. All patients had a favorable outcome. The locations of the treated tumors (eight left and five right) were central (two), upper pole (two), lower pole (three) and middle kidney parenchyma (six anterior, two posterior, and five peripheral). Mean tumor size was 3.3 cm (range 1.8-5 cm). Two WI (19 and 24 min) were needed. Immediate postoperative serum creatinine and CRP were elevated within 0.1 to 0.6 mg/dl (mean 0.18) and 2.1-10 mg/dl (mean 6.24), respectively. Coagulation depth ranged from <1 to 2 mm without an effect on histopathological evaluation of tumors or RR. One patient had positive RR. During follow-up (2-6 months), one patient developed an A-V fistula that needed embolization. This prospective in-vivo feasibility study showed that the diode laser is a safe and promising device for LPN. Its advantages are minimal gas formation, good hemostasis, and minimal parenchymal damage. Oncological safety appears to be warranted by the use of a diode laser.