Bromelain, a protease enzyme, is found in the stem and fruit of pineapple. It has been used in medical as therapeutic agents and supplements, and also known to have immunomodulatory function. However, as protease, it is concerned that bromelain will affect the mammalian cells that have proteins on their surfaces. The objective of this research was to find out the effect of bromelain on mammalian cells. In order to do so, mammalian cell culture was utilized with MT -2 cells (a T cell lymphocyte) and bromelain concentrations in culture medium were 25mg/ml, 20mg/ml, 10mg/ml, 5mg/ml, and 1 mg/ml, and the evaluation of cells was using MTT assay (three MTT assays). The high concentrations resulted in inhibition more than 50%. The concentration of 5 mg/ml from second and third assay had inhibition around 50% and 1 mg/ml had no inhibition and in turn had very good viability. Therefore, this research showed that bromelain concentration of 1 mg/ml to below 5 mg/ml (specific activity 3.001 U/mg) was safe for the MT -2 cells.