A method and apparatus for detecting a cell in a mobile communication system such as an LTE (Long Term Evolution) system are provided. In the method, when a signal is received from at least one base station, a primary synchronization channel (PSCH) detector detects a PSCH symbol in the signal. Then a PSCH validity determiner ascertains a valid value of the PSCH symbol and determines whether the valid value is greater than a given threshold. If the PSCH symbol is greater than the threshold, a secondary synchronization channel (SSCH) allocator estimates a position of an SSCH symbol in the signal using the PSCH symbol. Then an SSCH detector detects the SSCH symbol at the estimated position, so that a neighboring cell can be found through the detected SSCH symbol.