Abstract The production and capacity planning of a manufacturer in a supply chain facing seasonal demand is studied. A fuzzy mixed integer linear programming model is proposed for the manufacturer to find an ideal production and inventory level in each period such that the impact on capacity changing due to demand fluctuation is minimized. Using Verdegay's non-symmetric approach, the fuzzy model can be transformed to a parametric programming problem and solved by a general mixed integer linear programming package. Examples are included to illustrate the proposed model and its performance.