Fish meal is commonly used in the diets of fish, but its high cost and sustainability as a feed ingredient raise concerns. In order to reduce dependence on fish meal, proteins from plant sources are increasingly being recommended as an alternative ingredient in fish diets. The paper aims to examine whether risk attitudes and time preferences influence the decision to choose feed protein sources for intensively farmed fish. Using measures based on behavioural economics theories, we elicit risk attitudes and time preferences of 100 Nigerian fish farmers and estimate a double hurdle regression by assuming that fish farmers make their feed protein substitution decisions in two steps. The results indicate that risk-seeking farmers are less likely to substitute (risk-increasing) fish meal for plant-based proteins in fish feed. There is no statistically significant effect of time preference on the decision to substitute fish meal for plant-based proteins. Other results show that a higher level of education and income and a larger farm size positively influenced the decision to substitute fish meal for plant-based proteins, while male farmers were less likely to substitute fish meal for plant-based proteins. These findings suggest that farmers' risk attitudes, education, income, farm size, and gender are critical factors that policymakers and stakeholders should consider in interventions to encourage farmers to transition to more sustainable feed input.