Testosterone replacement therapy (TRT) has been investigated in older men as a preventative treatment against Alzheimer’s disease and dementia. However, previous studies have been contradictory. We assessed TRT physiological effects in 44 older men (aged 61 ± 7.7 years) with subjective memory complaints using a double blind, randomized, crossover, placebo-controlled study. Participants were randomized into 2 groups, one group received transdermal testosterone (50 mg) daily for 24 weeks, followed by a 4 week wash-out period, then 24 weeks of placebo; the other group received the reverse treatment. Blood evaluation revealed significant increases in total testosterone, free (calculated) testosterone, dihydrotestosterone, and a decrease in luteinizing hormone levels (p<0.001) following TRT. Although there were significant increases in red blood cell counts, hemoglobin and prostate specific antigen levels following TRT, they remained within normal ranges. No significant differences in plasma amyloid beta, estradiol, sex hormone binding globulin, insulin levels, body fat percentage, or body mass index were detected. This is the first carefully controlled study that has investigated the influence of TRT in Indonesian men on blood biomarkers linked to dementia risk. Our study suggests TRT is safe and well-tolerated in this Indonesian cohort, yet longitudinal studies with larger cohorts are needed to assess TRT further, and to establish whether TRT reduces dementia risk.