We report here on the early stage of the precipitation behavior of aged Al–Li–Cu alloys using transmission electron microscopy. The δ′ phase (Al 3Li, L1 2 structure (Structurbericht)) was found to exist in the as-quenched specimen containing 2.4 wt%-Li, whereas no precipitation was observed in the as-quenched specimen with 1.6 wt%-Li. After aging at 100 °C for 3 h, GP-I zones nucleated homogeneously in both specimens; but no δ′ phase was detected in the 1.6 wt%-Li alloy at that stage. As the aging proceeds, the δ′ phase nucleates and grows on the GP-I zones. The composite structure, in which the GP-I zone is flanked by a pair of lenticular δ′ particles, is stable in 180–200 °C. The facing lenticular δ′ particles on a GP-I zone were systematically found to be anti-phase with respect to each other.