The present study is aimed at studying the heat capacity of fish oil as an oil component for obtaining biodiesel fuel. One of the most promising renewable sources of raw materials for obtaining biodiesel fuel are microalgae. In terms of energy yield, microalgae significantly exceed palm and rapeseed oil, which are usually used to produce biodiesel. The scientific significance of the work lies in replenishing the database on the isobaric heat capacity of the substances under study. The practical significance is that the obtained data will be needed at the stages of modeling, optimization and scaling of the technology for producing biodiesel fuel from fish oil. Differences in the composition of fish oil for different fish species create the problem of insufficient study of their properties. The study of heat capacity was the main goal of this work. A scanning calorimeter (IT-s-400) with an automatic data collection system was used to measure the isobaric heat capacity of fish oil. The article presents new results of a study of the isobaric heat capacity of fish oil at high temperatures and pressures. The measurements were carried out in the temperature range from 298.15 to 473.15 K and at pressures up to 39.2 MPa. The expanded uncertainty of heat capacity measurements is 2.4%, pressure - 0.05%, and temperature - 15 mK at a confidence level of 95% and a coverage factor of k = 2. A comparison of the obtained and literature data in the studied area of state parameters was carried out. A comparison of the obtained data with the presented calculation according to the correlation equation at a temperature of 293 K and atmospheric pressure showed good agreement. For example, the specific heat capacities of raw fish oil differ from the data according to the equation by 8%, deresined by -6.7%, neutralized by -7.27%, bleached by -4% and deodorized somatic fat by 0.36%, respectively.