A control apparatus for an automatic transmission includes a running condition detector and a controller. a plurality of gear change stages include at least one specific gear change stage that has a specific transmission gear ratio, that involves at least one necessary engagement mechanism which needs to be engaged in order to obtain the specific transmission gear ratio, and that involves at least one no-change engagement mechanism which causes no change in the specific transmission gear ratio. Both of the at least one necessary engagement mechanism and the at least one no-change engagement mechanism are engaged during a time period from a timing to begin an operation to change a gear change stage to the specific gear change stage until a timing to complete the operation. The at least one no-change engagement mechanism is released after the timing to complete the operation.