Low-frequency noise properties of 100 nm-thick Langmuir–Blodgett (LB) films of stearic acid in a metal–insulator–semiconductor (MIS) structure have been studied as a function of frequency and leakage current. The excess noise is found to be consistently 1/f-like within a range of frequencies between 1 Hz to 1 kHz when leakage current is varied from 10⁻⁸ A to 10⁻⁴ A. The sources of noises are identified; the trap density is estimated to be 3.6 × 10¹⁸ m⁻² eV⁻¹.