An operation mode control system for an automatic automotive power transmission includes a manually operable mode selection switch for selecting an operation mode from among economy, power, and hold modes. When an acceleration demand magnitude is larger than a criterion value while the hold mode is selected, the execution of the hold mode is suspended. This suspension of the hold mode execution is automatically released without operating the manually operable mode selection switch when certain conditions are reached. The power mode may be executed in place of the hold mode during the suspension of the hold mode execution.