Lean premixed compression ignition combustion provides the potential for simultaneous reduction of NOx and PM, while imposing moderate penalties on CO and HC emissions. To overcome these drawbacks in existing premixed combustion modes of diesel engines, an ultramultihole (UMH) nozzle was developed in this study. The UMH nozzle has two layers of injection holes and a large flow area. Two sprays of the upper and lower layers meet in the space of the combustion chamber. A high-pressure common-rail fuel injection system was used in this experiment. The fuel injection rate of the UMH nozzle was measured using the constant volume method, and its spray pattern was recorded using high-speed digital photography. Combustion and performance experiments with the UMH nozzle were conducted on a turbocharged intercooled diesel engine. The results showed that the UMH nozzle exhibited a higher injection rate, shorter injection duration, shorter spray penetration, and bigger spray angle than those of the conventional nozzle. These characteristics facilitate better mixing of fuel and air prior to ignition, and thus NOx and PM emissions were simultaneously reduced with low CO and HC emissions by combining the UMH nozzle with EGR (exhaust gas recirculation).