The focus of this study is to reduce harmful NOx and soot emissions of a compression ignition (CI) engine using reactivity-controlled compression ignition (RCCI) with n-Butanol. RCCI was achieved with the port fuel injection (PFI) of a low reactivity fuel, n-butanol, and a direct injection (DI) of the highly reactive fuel ULSD #2 (Ultra Low Sulfur Diesel) into the combustion chamber. The reactivity, ID, and CD where determined using a Constant Volume Combustion Chamber (CVCC) where ID for n-butanol was found to be 15 times slower than ULSD. The emissions and combustion analysis was conducted at 1500 RPM at an experimental low engine load of 4 bar IMEP; the baseline for emissions comparison was conducted using conventional diesel combustion (CDC) with an injection timing of 16° BTDC at a rail pressure of 800 bar. RCCI was conducted utilizing 75% by mass PFI of n-butanol with 25% ULSD DI, showed a simultaneous reduction of both NOx and soot emissions at a rate of 96.2% and 98.7% respectively albeit with an increase in UHC emissions by a factor of 5. Ringing Intensity was also significantly reduced for Bu75ULSD25 (RCCI Experiment) with a reduction of 62.1% from CDC.