A control device for an automatic transmission includes a speed change controller configured to generate a speed change instruction. A temperature calculator is configured to calculate a temperature of at least one frictional engagement element among frictional engagement elements. A rotation difference calculator is configured to calculate a rotation difference between an input and an output of the at least one frictional engagement element. A determining unit is configured to determine whether the frictional engagement element is engageable or non-engageable based on the temperature and the rotation difference of the frictional engagement element and a pattern of the speed change instruction. The delay unit is configured to delay engagement until the determining unit determines that the frictional engagement element is engageable, if the determining unit determines that the frictional engagement element is non-engageable when the speed change controller generates the speed change instruction.