An apparatus and method for detecting a pilot signal in a mobile communication system are provided by which the processing time taken to demodulate a traffic channel based on a channel estimation result can be reduced, and thus, the size of a buffer for buffering signals until the presence of a secondary/auxiliary pilot signal is detected can also be reduced. The apparatus includes a first channel estimator for estimating a channel for a noise component of a pilot symbol received by a first receiver, a second channel estimator for adding a pilot symbol received by a second receiver and the pilot symbol received by the first receiver and estimating a channel for a noise component of the added pilot symbol, an energy detector for detecting an energy value of a pilot symbol using result values output from the first and second channel estimators, and a comparison and determination unit for determining whether or not there is a secondary/auxiliary pilot signal by using the detected energy values.