The effectiveness of multidomain training compared to cognitive or physical training alone has been controversial with some studies suggesting that combined interventions might produce synergetic effects. We conducted a three-level meta-analysis on the transfer effects of multidomain interventions versus cognitive and physical training alone. We obtained 1,070 effect sizes from 54 studies, involving 5.547 healthy older adults. Our results revealed a synergetic effect of multidomain training on executive functions, and larger effects on attention and memory than cognitive and physical training. Multidomain and single cognitive training produced similar effects on memory in comparison to physical training. We did not find differences in processing speed, verbal functions, and global cognition. Moderator analyses showed a complex pattern. In general, age, publication year, and study quality were not significant. We conclude that the combination of cognitive training with physical exercise could be a promising strategy to prevent cognitive and physical declines with aging.