This work presents a flexible coplanar-fed dual-band antenna built on Kapton polyimide substrate, tuned to cover the 2.45 GHz and 5.8 GHz Industrial, Scientific, Medical (ISM) bands. The influence of two types of deformations on |S11| was studied both through simulations and measurements. The considered deformations are bending and crumpling. Results for this prototype show that |S11| is particularly robust to deformation, except for the most extreme cases of crumpling and at the highest frequency band. However, these severe crumpling conditions are not expected to easily occur in real usage scenarios. Due to its flexibility and characteristics the proposed antenna is suitable to be used in wearable applications.