This article analyzes and criticizes the transcendental arguments Roy Bhaskar uses to justify his transcendental realist ontology. They are compared to Kant's in the Critique of Pure Reason and a detailed reconstruction of those formulated in A Realist Theory of Science is presented. It is argued that these formulations contain certain ambiguities and are beset with other, more serious, problems. First, Bhaskar's descriptions of scientific practices are far more controversial than is presupposed in his arguments. Second, Bhaskar uses the Kantian concept of transcendental necessity in his transcendental arguments which inevitably connects them to certain Kantian doctrines that are inconsistent with his transcendental realist ontology. Some qualifications of his formulations Bhaskar made in his later writings are also considered and another possible interpretation of his transcendental arguments is presented from the point of view of these qualifications. On this interpretation, Bhaskar seeks to naturalize Kantian transcendental arguments by combining a posteriori premises with a priori philosophical reasoning. It is argued that this kind of naturalized version of transcendental arguments is also problematic. Therefore, it is concluded that Bhaskar's transcendental arguments fail to justify his transcendental realist ontology. Nevertheless, it might be possible to justify at least some of Bhaskar's ontological claims from the perspective of meta-philosophical naturalism. It is maintained that this requires naturalization not just of transcendental arguments but of the whole transcendental realist ontology. One possible form of naturalistic argument that might replace Bhaskar's problematic transcendental arguments is sketched. It is, however, admitted that, desirable though the naturalization of Bhaskar's early ontology may be, more work needs to be done to achieve this goal.