BACKGROUND AND PURPOSE: Mild cognitive impairment (MCI) may be a precursor to dementia; however, its progression may be prevented or slowed with exercise. This study aimed at determining the effects of group aerobic and strength training on cognition, conditioning, muscle endurance, and balance in underprivileged community-dwelling older adults with MCI. METHODS: This was a single-blind, randomized, and matched-pair controlled (gender, age, body mass index, and Addenbrooke's Cognitive Examination-Revised for MCI diagnosis) clinical trial. It was developed in 4 community centers. Fifty-two sedentary, functionally independent individuals, aged 60 years or more, with MCI were randomized into intervention group (n = 26) and control group (n = 26). Participants were tested before and after a 24-week exercise program. Sociodemographic characteristics, cognition (Mini-Mental State Examination), conditioning (2-minute stationary walk test), lower-limb endurance (30-second sit/stand test), and balance data (Functional Reach test) were collected. The intervention group walked and exercised twice weekly (60 minutes each) using ankle weights, latex resistance bands, and dumbbells. The exercise load and intensity were regularly increased on the basis of a preestablished incremental number of sets and repetitions and on the basis of the participants' correct movement execution with a given load. Data were analyzed with Pearson χ test, Fisher exact test, Student t test, Mann-Whitney U test, 2-way repeated measures analysis of variance, and the Cohen d. RESULTS AND DISCUSSION: Before the intervention, no significant differences were found between groups for any of the variables. Postintervention, significant differences were observed in cognition, conditioning, muscle endurance, and balance. Significant time-by-group interactions were detected in all the intergroup analyses. The improvements observed in the intervention group had medium to large effect sizes (0.35-1.15). The control group's decrease in cognition (13.9%) had a large effect size, while its Functional Reach test decrease (11.4%) had a medium effect size, with no significant change in conditioning or muscle endurance. CONCLUSION: The training program improved cognitive function, muscle endurance, aerobic conditioning, and balance in older adults with MCI.