Many of the world’s most successful and noxious invasive plant species exist as polyploids in their non-native range and many biological invasions begin in urban areas characterized by high levels of eutrophication. Furthermore, recent evidence suggests that polyploids or organisms with larger genomes may experience fitness and growth advantages under nutrient enrichments, yet we lack information on whether soil nutrient conditions alter the likelihood of polyploid invasive species success in non-native habitats;  areas where competition should be prioritized over defense against herbivores as antagonistic interactions are often diminished in invasive ranges. Solidago gigantea (Giant goldenrod) is a widespread polyploid complex that is native to North America where it occurs in diploid, tetraploid, and hexaploid forms but is a noxious invader in Europe and Asia, where only tetraploid cytotypes have been observed. We grew diploid, native-tetraploid, and invasive-tetraploid plants of S. gigantea in a greenhouse in either ambient or enriched soil nitrogen (N) and phosphorus (P) treatments to test whether unique gene expression patterns and traits (1) give native-tetraploids an invasive edge over diploids, especially in enriched NP conditions (preselection differences), and/or (2) exist between native and non-native tetraploid populations as a result of post-introduction selection (post-selection differences). Specifically, we examined gene expression patterns and phenotypic traits related to growth, physiology, and foliar defensive chemistry. We found that in comparison to diploids, native-tetraploids downregulated more photosynthesis and terpene synthesis-related transcripts and upregulated more growth-related transcripts under ambient NP conditions, but that in enriched conditions most transcriptome differences disappeared although native-tetraploids continued to downregulate more terpene synthesis-related transcripts. Phenotypic trait differences mostly matched transcriptome expression differences in that diploids had greater photosynthetic rates and produced more defensive compounds regardless of NP treatments, although native-tetraploids had significantly larger above- and belowground biomasses than diploids. In contrast to native cytotype comparisons, we found very little transcriptome and phenotypic trait differences among native and non-native tetraploids. In fact, the only significant differences observed were that non-native tetraploids had greater mean belowground biomasses than native-tetraploids, which could have existed before introduction or been selected for from existing genetic variation. Our finding suggests that the unique tetraploid gene expression patterns and phenotypic traits may be advantageous over diploids in non-native environments, especially if the downregulation and reduction of defense compounds allows tetraploids to conserve and/or re-allocate resources towards competitive attributes in environments where defensive investment may not be needed. Additionally, the similarity in gene expression patterns and phenotypic traits between native and non-native tetraploids implies a lack of post-introduction selection pressures, insufficient evolutionary time for change, and/or the presence of founder effects in non-native populations. However, larger belowground biomasses could provide advantages to perennial invader in new variable environments. This study is among the few to compare transcriptomic data between native and non-native geo-cytotypes and offers valuable insights into the molecular methods underlying successful biological invasions both pre- and post-introduction.