Purpose: To evaluate the effect of inherent and incidental magnetization transfer (MT) on T1 and T2 measurements when using the mixed turbo spin echo sequence (mixed-TSE). Methods: mixed-TSE was applied to a phantom of 1-5% agarose gel. The levels of the MT effects were induced and controlled by varying the number of slices per acquisition package. Results: T1 values were underestimated in multi-slice mixed-TSE. No obvious trend was observed for T2 measurements. Conclusion: mixed-TSE is powerful and efficient tool for qMRI, yet caution should be taken when interpreting the derived T1 values because of MT effects.