Knowledge and competencies traditionally rooted in industries external to the food sector’s boundaries are gaining momentum and foster innovation in the food domain. In Italy, food companies collaborate with other firms in open and cross-industry innovation (CII) projects to achieve a competitive advantage. The paper aims to shed lights on eventual drivers for CII in the food sector in a twofold manner: (i) exploring to what extent external knowledge sourcing affects innovation and (ii) seeking to understand to what extent different means of external knowledge sourcing might differ according to the company size. To this end, probit models have been run on a sample of 703 Italian food companies from the CIS 2010 and 2012. Empirical evidence shows that in the Italian food industry innovation relies on different external knowledge sources. Acquisition of machinery and equipment allows food companies to transfer external know-how inside the firm boundaries. Product innovation benefits of external R&D activities as well as of information provided by competitors and consultants. Process innovation relies mostly on acquisition of technology (machinery and equipment) as well as on information provided by input suppliers.