The deformation of a slender bubble in a non-Newtonian liquid in a simple extensional and creeping flow has been theoretically studied. Assuming a constant pressure in the liquid, the deformation of the bubble is described by a single ordinary differential equation, which was solved numerically. Analytical expressions for the local radius were obtained near the center and close to the end of the bubble. The results for the shape of the bubble are presented as a function of the capillary number and type of liquid.