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There is a paucity of comprehensive air quality data from urban areas in the Middle East. In this study, portable instrumentation was used to measure size-fractioned aerosol number, mass, and black carbon concentrations in Amman and Zarqa, Jordan. Submicron particle number concentrations at stationary urban background sites in Amman and Zarqa exhibited a characteristic diurnal pattern, with the highest concentrations during traffic rush hours (2−5 × 10⁴ cm^−3 in Amman and 2−7 × 10⁴ cm^−3 in Zarqa). Super-micron particle number concentrations varied considerably in Amman (1−10 cm^−3). Mobile measurements identified spatial variations and local hotspots in aerosol levels within both cities. Walking paths around the University of Jordan campus showed increasing concentrations with proximity to main roads with mean values of 8 × 10⁴ cm^−3, 87 µg/m³, 62 µg/m³, and 7.7 µg/m³ for submicron, PM₁₀, PM_2.5, and black carbon (BC), respectively. Walking paths in the Amman city center showed moderately high concentrations (mean 10⁵ cm^−3, 120 µg/m³, 85 µg/m³, and 8.1 µg/m³ for submicron aerosols, PM₁₀, PM_2.5, and black carbon, respectively). Similar levels were found along walking paths in the Zarqa city center. On-road measurements showed high submicron concentrations (>10⁵ cm^−3). The lowest submicron concentration (<10⁴ cm^−3) was observed near a remote site outside of the cities.