Wormholes (WHs) require negative energy, and therefore an exotic matter source. Since Casimir energy is negative, it has been speculated as a good candidate to source those objects a long time ago. However, only very recently, a full solution for [Formula: see text] has been found by [R. Garattini, Eur. Phys. J. C 79, 951 (2019), doi:10.1140/epjc/s10052-019-7468-y] thus the Casimir energy can be a source of traversable WHs. Soon later [G. Alencar, V. B. Bezerra and C. R. Muniz, arXiv:2104.13952 [gr-qc]] have shown, that this is not true in [Formula: see text]. In this paper, we show that Casimir energy can be a source of the Morris–Thorne WH for all spacetime with [Formula: see text]. Finally, we add the cosmological constant and find that for [Formula: see text] Casimir WHs are possible, however, the space must always be AdS. For [Formula: see text], we show that the cosmological constant invert the signal with increasing throat size.