Purpose: This paper aims at assessing the alignment of eight of the Life Cycle Initiative’s ten principles for life cycle sustainability assessment (LCSA) and the LCSA practice as well as the challenges to reaching the full implementation of the principles as a basis for a harmonized framework. Materials and methods: To understand the extent of alignment of existing LCSA studies with the principles, 193 case studies published before the Life Cycle Initiative’s ten principles’ publication were identified. Their levels of alignment were assessed against the criteria designed per principle: full, medium, or no alignment. The principles of “materiality of the system boundaries” and “consistency” could not be assessed as most studies lacked related background information; hence, no objective nor systematic criteria could be designed. Results: The alignment of practice with the principles is variable: The vast majority of studies cover the 3 pillars (principle 3 on completeness). Principle 9 (communication of trade-offs) is well addressed in the case studies. Principles 2 (alignment with the phases of ISO 14040: 2006 standard), 4 (taking into account perspectives of key stakeholders), and 8 (transparency) were not properly addressed in a majority of case studies. Principles 1 (understanding the areas of protection and impact pathways), 5 (taking into account product utility beyond functional unit (co-benefits)), and 10 (caution when compensating negative and positive impacts) remain to be implemented as some methodological challenges have to be overcome. Principles 6 and 7 were not assessed. Conclusions: LCSA is gaining momentum due to the communication and dissemination of LCSA among practitioners, potential users, and decision-makers in the public and private sectors. However, some key challenges remain for reaching the implementation of the principles: understanding of the inter-relationships between the three dimensions of sustainability to build impact pathways and select relevant impact categories for LCSA, guidance for communicating trade-offs and decision-making based on LCSA, and generalizing the (open) access to publications and related supplementary information.