This study investigates the integration of generative artificial intelligence (AI) into the professional practices of Japanese freelance information technology (IT) engineers. To support the analysis, an entrepreneurial orientation index was employed in the survey. Moreover, this study examines the use of generative AI between two groups: those who consider freelancing a primary occupation and those who consider it a secondary occupation. An ordered logistic regression analysis investigates the factors associated with a decision-making style rooted in effectuation, a concept commonly tied to entrepreneurial behavior. The responses of the questionnaire survey indicate that freelance IT engineers who consider freelancing as their primary occupation are likelier to adopt generative AI in their professional activities than those who view it as a secondary occupation. An ordered logistic regression analysis revealed that in the primary occupation group, higher engagement with generative AI was significantly associated with a tendency toward causation orientation. However, the secondary occupation group showed no statistically significant relation with effectuation orientation.