© 2022, Akadémiai Kiadó, Budapest, Hungary.One of the most commonly used techniques in heat transfer enhancement studies is loose-fit twisted tape with variety of configurations. Optimizing the configurations prevents additional effort, time and cost losses. In this regard, the current research examined the impacts of design parameters identified as twist ratio, clearance ratio, and Reynolds number of the loose-fit twisted tape with trapezoidal wings used in a heat exchanger pipe on pressure drop and heat transfer. For the optimization study, the impacts of three various twist and clearance ratios, and six various Reynolds numbers on the friction factor, Nusselt number, and thermohydraulic performance factor identified as performance parameters were evaluated. The optimum conditions were revealed by conducting the signal-to-noise ratio analysis of the Taguchi method for the purpose of maximizing/minimizing the response variables on an individual basis. As methodology, multi-criteria decision-making problem was applied because of the optimum conditions depending on many variables and various response variables. The solution of the multi-objective optimization problem was provided by employing a pair of methods of the AHP/ TOPSIS. The analysis of variance was performed to determine the extent to which every parameter contributed to the response variables. According to the ANOVA findings, the most effective parameter was the Reynolds number. The Reynolds number of 18000, the twist ratio of 2, and the clearance ratio of 0.0178 were chosen as the multi-objective optimum conditions. In relation the results, an approach regarding the optimum design parameters, which has not been revealed before in the use of loose-fit twisted tape, has been put forward.