Outsourcing is the action of contracting a specific task, function, or process to an external company instead of using an organisation's resources. The history of outsourcing goes back to the 1980s when it was used for cost reduction in non-core business operations. Over time, outsourcing has moved to more strategic areas and has become an important factor in business performance. The selection of the best alternative among alternative outsource manufacturers is a multi-criteria decision-making problem. In this study, the fuzzy set theory is used to capture the uncertainty embedded into the decision problem. In this paper, an interval-valued intuitionistic fuzzy Analytic Hierarchy Process and Technique for Order of Preference by Similarity to Ideal Solution-based methodology is proposed, and an application is provided for the evaluation of outsource manufacturers.