This paper reports the discovery that free-standing rubbery fiber mats can be electrospun from polyisobutylene-based thermoplastic elastomer/poly(ethylene glycol) mixtures from a THF-toluene solution. Direct contact and elution cytotoxic assays of these mats showed no cytotoxic response. Electrospinning the polymers mixed with Zafirlukast (ZAF), an anti-inflammatory drug, resulted in complete encapsulation of ZAF into the fibers, without the need of coaxial spinning. Release profiles followed close to a Fickian diffusion model. Significantly, ZAF-eluting fiber mats successfully inhibited the target cysteinyl leukotriene receptors in vitro, known to reduce inflammation. Local application of these mats could have the potential to reduce capsular contracture, the major complication reported for silicone rubber breast prostheses due to inflammatory response. A recent study using a poly(lactic-co-glycolic acid) polymer coating with a similar drug demonstrated capsule thickness reduction in vivo, but suggested that higher doses and slower release rates would be more effective. We believe our slower releasing mats with higher loading could be better at mitigating capsular contracture.