In this work, silver microrods decorated-reduced graphene oxide (AgmR-rGO) composite was prepared and used for ammonia vapor sensing. The decoration of silver microrods on rGO is characterized by powder X-ray diffraction, UV–Visible spectroscopy, FT-IR spectroscopy, and field emission scanning electron microscopy. The length of microrods in the composite varies from 2.5 μm- 4.5 μm and the thickness is about 1.5 μm. The prepared AgmR-rGO sample was coated over the flexible polycarbonate membrane by the vacuum filtration method. The flexible film was used for NH3 vapor sensing with different concentrations; the response and recovery times of the sensor are calculated as 54 s and 41 s, respectively for 100 ppm of NH3 vapor. The limit of detection of the sensor towards the ammonia vapor is calculated as 0.19 ppm by a linear fit of the response curve. From the I-V characterizations, the fabricated film exhibits ohmic behavior.