Abstract. This research proposes part-family and machine-cell formation in a manufacturing cell design with the consideration of duplicated machines. In existing methods, part families and machine cells are firstly determined. Then, the incidence matrix of the cell formation is reconsidered for assignment of the duplicated machines. These ways are difficult and complicated. Moreover, they not guarantee for efficient solutions. So, the effective fuzzy multi-objective assignment model is developed for solving the cell formation problem with simultaneous assignment of the duplicated machines. Two crucial performance measures of a perfect grouping called exceptional elements and void elements, are considered and applied to the proposed model. Preemptive fuzzy goal programming is also used. Significant constraints are applied for enhancing the duplicated machine assignment process. Then, the decision maker can easily solve the cell formation problem and assign the duplicated machine, simultaneously. Adjustment to find the preferred solutions can be effectively done. The numerical example is also demonstrated to show the easiness, efficiency and flexibility of the proposed model. Keywords: cell formation; duplicated machines; cellular manufacturing system; perfect