Wormholes (WH) require negative energy, and therefore an exotic matter source. Since Casimir energy is negative, it has been speculated as a good candidate to source that objects a long time ago. However only very recently a full solution for D = 4 has been found by Garattini , thus the Casimir energy can be a source of traversable WHs. Soon later Alencar et al  have shown, that this is not true in D = 3. In this paper, we show that Casimir energy can be a source of the Morris-Thorne WH for all spacetime with D > 3. Finally, we add the cosmological constant and find that for D = 3 Casimir WHs are possible, however, the space must always being AdS. For D > 3, we show that the cosmological constant invert the signal with increasing throat size.