The presented study investigates the application of MnO2/3MgO nanocomposite, as a new sorbent for solid phase extraction and determination of trace amounts of Pb2+ and Cu2+ from various samples using flame atomic absorption spectrometry. After extraction, the analytes were desorbed using 0.01 M ethylenediaminetetraacetic acid. The effects of various parameters were studied and optimized. Under optimized experimental conditions the linear dynamic ranges for Cu2+ and Pb2+ were 10‒900 and 30‒900 μg/L, respectively, with a preconcentration factor of 20. The detection limits of Cu2+ and Pb2+ were 4 and 11 μg/L, respectively, and relative standard deviations for eight determinations of 100 μg/L were 3.6 and 3.8% for Cu2+ and Pb2+, respectively. The method was successfully applied for determination of copper and lead in mushrooms, rice, tap water and refinery wastewater with good spike recoveries ranging between 95‒106%.