Despite the existence of a formal process for making readmission agreements, researchers have observed an increasing reliance on non-binding readmission arrangements since 2016. These informal arrangements eschew procedures explicitly laid out in the Treaties and sideline the European Parliament in their creation and monitoring. This so-called informalization stands in contrast to the post-Lisbon Parliamentarization trend described in previous literature. It remains unclear, however, the extent to which informalization hampers Parliamentary influence in practice. In this paper, we analyze the degree of Parliamentary influence on content, implementation and broad policy rationale of readmission policy since the entry into force of the Lisbon Treaty, explicitly comparing Parliament’s behavior in the context of formal readmission agreements with its conduct in informal readmission arrangements. Our findings, based on data spanning the period 2010-2022 and including a wide range of policy documents as well as records of Parliamentary hearings, indicate that Parliamentary influence on informal readmission arrangements has been very limited, including because of Parliament’s reluctance to challenge practices of the EU executive through all the means at its disposal. At the same time, our findings also suggest that Parliament, in spite of its veto power and in contrast with other policy fields, already yielded limited influence over formal agreements as well as more general readmission policy. These findings question the argument of the legal literature on the impact of legal developments (both legalization and de-legalization, or informalization) on the actual power and influence of the European Parliament, and call for further research into exploring the reasons for limited Parliamentary influence in readmission policy.