In the present study, different turning operations (conventional, ultrasonic-assisted and hot ultrasonic-assisted operations) of Ti6Al4V alloy were investigated by using a new multi-criteria decision-making method. In the first part of the study, conventional turning, UAT and HUAT operations were conducted, and they were compared to each other. The modal/chatter tests were performed through a hammer and recording chatter sound. Cutting velocity (10–40 m/min) and cutting tool overhang lengths (60 and 70 mm) were used as cutting parameters in the experiments. The full factorial experimental design was used. In the comparison of the turning operations, surface roughness, stable cutting depths and maximum cutting tool temperatures were considered. Also, variance analysis was carried out to optimize machining outputs. In addition, chip formation was observed. In the second part of the study, multi-criteria decision-making (MCDM) analysis was performed by using reference ideal method which has been recently presented in the literature to optimize machining outputs. Surface roughness, stable cutting depths and maximum cutting tool temperatures were selected as criteria to rank all the experiments. Based on MCDM results, higher cutting speeds, lower tool overhang lengths and ultrasonic-assisted turning are the appropriate levels of the cutting parameters. As a result, this study helps to understand new non-traditional machining methods in terms of MCDM perspective.