BACKGROUND: Lactococcusis disease due to Lactococcus garvieae, one of the most important zoonotic bacterial diseases. Objectives: The purpose of this study was to evaluate the effect of Cinnamon essential oil and Nisin on the growth of Lactococcus garvieae. Methods: The effect of cinnamon essential oil with concentrations of 0, 0.25 and 0.75%, and Nisin 0, 0.4 and 0.8 μg/mL on growth of this bacteria at 4 and 8 °C during 0, 3, 6, 9, 12, 15 days of storage was investigated. Results: The results of this study showed that on samples kept at 4 °C, bacterial growth was delayed until the fifteenth day using cinnamon essential oil or Nisin, and in the case of cinnamon, the growth rate of bacteria in the ninth and fifteenth days was below 2 log cfu/g. While the combination of 0.8 μg/ml Nicin and 0.75% essential oil of cinnamon postponed growth on the third day. At 8 °C, Nisin, the cinnamon essential oil alone and in combination (similar to 4 ºC) until the sixth day prevented bacterial growth. Compared to the control treatment, the concentration of Nisin and cinnamon essential oil had a significant difference in inhibitory bacterial growth (P<0.05). The results also showed that the combination of Nisin and cinnamon essential oil, had a significantly higher effect than their single state. Conclusions: Results indicate that Nisin and cinnamon essential oil effectively inhibit the growth of Lactococcus garvieae in the rainbow trout fillet.