  In this paper, we calculate the weak deflection angle by Casimir wormhole and
its shadow. To do so, we derive the Gaussian optical curvature and use the
Gauss-Bonnet theorem. Then we find the deflection angle by Casimir wormhole in
weak field limits. Moreover, we obtain the weak deflection angle in the
presence of plasma medium and see the effect of the plasma medium on the weak
deflection angle. Moreover, we study a shadow of Casimir wormhole and we plot
and discuss them. We show the shadow of Casimir wormhole's behavior when
changing the value of $a$.
