This study investigates the application of a pilot signal in an orthogonal frequency division multiplexing (OFDM)-intensity modulated optical wireless communication system to reduce the peak-to-average power ratio (PAPR). The pilot-signal-phase selection is based on a selected mapping (SLM) algorithm. The maximum-likelihood criterion is used to estimate the pilot signal at the receiver. In a reliable communication link with a bit error rate (BER) of less than 10 -3, the BER of the pilot-assisted optical OFDM system is basically the same as that of the basic optical OFDM system (without pilot and PAPR reduction technology). Under the condition of a high-order (magnitude M>4) constellation, the pilot-assisted PAPR reduction technology is superior to the traditional SLM technology. Compared with the basic optical OFDM system, the pilot-assisted optical OFDM system can reduce the PAPR by approximate 2.5 dB under suitable conditions. Furthermore, the pilot-assisted optical OFDM system can reduce PAPR more effectively at a moderate point of M=64 and a complementary cumulative distribution function of 10 -4, without reducing the system's error performance.