Atlantic cod (Gadus morhua) were held either at seasonal ambient temperatures (-0.3 to 11°C) or at a relatively constant control temperature (8 to 11°C) to investigate aspects of protein synthesis during a period of compensatory growth. The rate of protein synthesis, total RNA and RNA specific rate of protein synthesis were determined in white muscle and liver when ambient temperatures were -0.3, 4.5 and 11°C in February, June and July, respectively. To allow for comparison between treatment temperatures, fish were also acutely transferred to a comparable assay temperature in February and June. Over the transition from 4.5 to 11°C (June to July), the ambient held cod had a significant increase in size, and substantially higher growth rate relative to control held fish over the same period; consistent with cold induced compensatory growth. During the onset of this enhanced growth, in June when ambient temperature was approximately 4.5°C, ambient held fish elevated the capacity for protein synthesis in the white muscle and liver via elevation of the RNA content of tissues. When ambient temperature reached the same point as the control fish (11°C); the rate of white muscle protein synthesis remained higher in the ambient than the control held fish, facilitated by elevated RNA content and greater RNA specific rate of protein synthesis, whereas all measured characteristics of protein synthesis in the liver were the same for ambient and control fish in July. The latter suggests that compensatory growth may be in part explained by improved efficiency of protein synthesis.