The purpose of this paper is the assessment of the ISO 14001:2015 transition process among Portuguese ISO 14001 certified organizations, including those that successfully have already achieved ISO 14001:2015 certification. A considerable number of the surveyed companies proceeded with the transition to the ISO 14001:2015 by introducing slight adjustments and were supported by external consultants. Nearly all of the respondent companies (97%) intend to transition until 15th September 2018. The highest ranked reported benefit is the “integrated approach with other management sub-systems” with a well-consolidated perception from the surveyed companies. This is aligned with the ISO 14001:2015 goal of improving the compatibility of management standards supported on the Annex SL. “Alignment with business strategy”, “improved top management commitment” and “improved internal and external communication” are also perceived to obtain significant benefits from ISO 14001:2015. The statistical tests carried out (Kruskal–Wallis) confirmed that the perception of some achieved ISO 14001:2015 certification benefits is dependent on the size of the organization. Concerning the motivations to proceed with certification, results suggest that there is not a particular company profile that is compelled to certify their EMS based on a specific type of motivation (Internal or External). Due to ISO 14001:2015 novelty, these exploratory results should be subjected to additional research confirmation.