An intelligent reflecting surface (IRS)‐aided visible light secure communication system is investigated. In order to improve its security performance, a power splitting scheme is adopted at the light‐emitting diodes. In contrast to most current research on the physical‐layer security in IRS‐aided visible light secure communication systems where secrecy rate or secrecy capacity maximization problems subject to various resource constraints were formulated, this letter takes the reliability of secure transmission into account. The closed‐form expression of secrecy outage probability is derived based on the statistical characteristics of the signal‐to‐noise ratio of the legitimate user, and the effects of light‐emitting diodes and IRS parameters and power splitting ratio on the secrecy outage probability are validated through simulations.