Thin film solar cells offer several benefits over conventional first-generation technologies including lighter weight, flexibility, and a wider range of optoelectronic tunability. Their environmental impact however needs to be investigated comprehensively to provide a clear comparison point with the first generation photovoltaics currently dominating the market. The main objective of this review is to evaluate current Life Cycle Assessment (LCA) studies conducted on thin film solar cells, highlighting the key parameters considered including life cycle stages, impact categories, and geographical locations. This included both commercially available thin film solar cells (a-Si, CIGS, CIS, CdTe, GaAs and GaAs tandem) as well as emerging (PSC, PSC tandem, DSSC, OPV, CZTS, QD) ones. A critical assessment of the results of 58 LCA studies was conducted and compared with traditional silicon based solar cells. Results indicate that emerging thin film solar cells hold great promise, as they tend to perform better than commercially available ones in the specified indicators, especially for CZTS and OPV. The assessment demonstrated that overall thin film solar cells had less energy requirement and better environmental performance than conventional crystalline silicon solar cell systems. However, due to their lower efficiencies their energy payback time was higher. This review provides a benchmark for the environmental LCA of different thin film solar cell technologies in order to highlight the relevance of these devices for sustainable energy generation and to give manufacturers and LCA experts information and a basis for future evaluation of solar cells.