Abstract Thermal expansion (Δα) of mixed valence systems in the presence of crystalline electric field (CEF) has been investigated in the framework of Anderson model as studied earlier by Coqblin and co-workers. The Δα has been analysed in two limiting cases of temperature. In the low temperature limit it is found to be proportional to T and in the high temperature limit the proportionality is T -2. The contribution to Δα goes through a maximum. The effect of CEF is to increase the value of Δα which reveals a qualitative change in the thermal expansion. Qualitatively, Δα is estimated by choosing proper values of T and δ. For a typical case with T ≌ 100 K, δ ≌ 200 K; Δα is found to be an anomalously large value of the order of 8 × 10 -3 K -1.