As one of the most widely used integrated circuit (IC) lead frame materials, Cu-2.1Fe alloy (C19400) shows excellent comprehensive properties, such as 90° bend fatigue, 90° bend formability, corrosion-proof, solder ability and resistance of solder peeling off. As a successful medium-strength and high-conductivity copper alloy, the Cu-2.1Fe alloy is strengthened by precipitation hardening and work hardening. Metastable coherent g-Fe particles will precipitate from supersaturated copper matrix during aging. The effects of long-term aging at different temperatures on the g-Fe coarsening characteristics and the mechanical properties of Cu-2.1Fe alloy were investigated, by means of conventional TEM, SEM, hardness, tensile strength and electrical conductivity testing. The results show that solution-treated Cu-2.1Fe alloys can reach its peak hardness and maintain for a longer time when aging at 500 ℃. The maximum of strength occurred at a particle size of about 12 nm in mean diameter. The coarsening kinetics of g-Fe follows Lifshitz-Slyozov-Wagner (LSW) theory and the activation energy for growth is estimated to 222 kJ/mol. Furthermore, it is found that coherent Fe particles gradually evolve into semi-coherent and cubical particles after aging for a long time and at high temperatures. The aging strengthening effect of Fe particles is not significant, and the maximum increment of stress is about 100 MPa. The strengthening mechanism of undeformed Cu-Fe alloy is coherency strengthening during the under-aged stage and changes to Orowan mechanism during the over-aged stage. Experimental results are in agreement with theoretical predictions.