Introduction: Tempeh consumption has been linked to the improvement of cognitive function in older people. However, to what extent the amount of microorganism or the size of tempeh serving consumed per day influences the benefit to cognitive functions has not yet been studied. Methods: This experimental study involved a total of 90 respondents, who were divided into 3 groups: group A (consuming 100 g of Tempeh A/day), group B (consuming 100 g of Tempeh B/day), and group C (control). Intervention was given for 6 months. Cognitive assessments were done before and after the intervention. Blood uric acid level was checked at the end of intervention to examine the effect of tempeh consumption on this. The inclusion criteria were respondents aged 60 years or over with mild cognitive impairment (MCI) who agreed not to consume other fermented food during the study period. Respondents with diabetes were excluded. Results: There were 84 subjects at the end of the study, majority being female (71.4%) and aged over 65 years (72.6%). An increase in global cognitive scores was found in both groups A and B. The increase in language domain scores was found only in group A. Conclusion: Both Tempeh A or Tempeh B consumption for 6 months appeared to be beneficial in improving global cognitive function of older people with MCI. Consuming Tempeh A, which had a lower number of microorganisms, was also associated with an improvement in the language domain.