An integrated performance analysis of a vanadium-based urea-SCR system used for the reduction of exhaust emissions from a diesel engine was carried out. The engine was run on an AC electrical dynamometer in accordance with an 8-mode steady-state cycle. The number-size distribution of particles and carbonyls was analyzed using an electrical low pressure impactor (ELPI) and high performance liquid chromatography (HPLC), respectively. It was found that conversion and/or reduction efficiency (RE) of the SCR were highly affected by the catalyst temperature and space velocity (SV). The NOx pollutants were greatly reduced with the decrease in SV within the load modes of cyclic speeds. The SCR exhibited an RE of more than 50% for NOx emissions at 321-435 °C, while the maximum RE was 80.5%. Total hydrocarbon (HC) emissions were also increased with the decrease in load for both cyclic speeds, while the RE varied from 38.7% to 71.1%. Significant increases in upstream and downstream carbon monoxide (CO) emissions were noticed with the decrease in engine load. Reluctance to reduction or a negative RE, ranging from 1.5% to 72%, was observed for CO emissions with the SCR. In addition, nanoparticles were greatly reduced, whereas particles of the size range 57-255 nm showed less reduction. The number-size distribution of particles was shifted from smaller to larger sizes with the SCR retrofit. Furthermore, a substantial conversion of up to 55.3% was obtained in the case of carbonyl emissions. The maximum RE was 58%, 67%, 50%, and 64% for formaldehyde, acetaldehyde, acrolein and acetone, and propionaldehyde, respectively