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Chemical identification of microplastics is a crucial step in understanding the sources of microplastics and studying the effects of microplastic pollution. A major challenge to microplastics identification is that weathered microplastics undergo surface chemical changes that differ from their unweathered counterparts which hinders spectroscopic matching and thus identification. While IR spectroscopy is a common technique used for microplastics identification, Raman spectroscopy is a complementary technique and its higher spatial resolution capabilities (capable of analyzing particles as small as 1 μm) make it a popular tool to identify smaller microplastics that can otherwise go undetected by IR techniques. Currently, there is limited Raman spectroscopic information on weathered microplastics. Herein, we investigate the effects of artificial weathering on polyethylene and polypropylene microplastics for 0–26 weeks in four different weathering conditions (air, DI water, artificial seawater, and Puget Sound seawater) using Raman and IR spectroscopy. Microplastics weathering in different environments reveal that they can lead to different IR spectra, suggestive of varying degradation pathways for plastics, but relatively similar Raman spectra. Raman spectra, however, do show variations in peaks associated with the crystallinity and amorphous regions in the polymers which indicate morphological changes in the weathered microplastics. Overall, Raman spectroscopy acts as a practical interrelated method that can be used in lieu of IR spectroscopy in cases where weathering can complicate plastics identification by spectroscopic matching. This work aims to provide spectral information to facilitate marine microplastic chemical identification and encourage more investigations on the conditions that influence microplastic weathering.