The surge in online shopping, catalyzed by the COVID-19 pandemic, has reshaped consumerbehavior worldwide. Ecommerce platforms account for a substantial portion of retailtransactions, and as the digital marketplace continues to expand, the allure of ultra-fastecommerce platforms such as Shein, Temu, and AliExpress grows exponentially. Theseplatforms offer an extensive array of products at unprecedented response to immediate trendsand affordability, leveraging aggressive marketing strategies to capture consumer attention.However, the convergence of ultra-fast ecommerce raises concerns about environmentaldegradation, unethical production practices, and labor exploitation. Brands operating withinthis business practice often prioritize profit margins over sustainability, perpetuating a throw-away culture that undermines efforts towards ethical consumption. The environmental andsocial implications of this rapid consumption trend remain underexplored, and what this mixed-method study aims to investigate is the intricate relationship between ultra-fast ecommercemarketing tactics and consumer sustainability beliefs, focusing on Swedish consumers. Afterextensive literature review and empirical research involving a survey of 122 consumers and 6follow-up interviews, this study examines the multifaceted influences of ultra-fast ecommercemarketing on Swedish consumers' shopping behaviors and sustainability attitudes. Ourinvestigation focuses on the complex interplay between price consciousness, impulsiveness,trend seeking and opinion seeking behavior, and the persuasive power of marketing tacticsemployed by ultra-fast ecommerce platforms. Our findings suggest that while Swedishconsumers express a strong commitment to sustainability in principle, the attraction of lowprices often eclipses environmental and social considerations when making purchasingdecisions on ultra-fast ecommerce platforms. Marketing strategies such as paid advertising,influencers, UGC, and aggressive discounts play a pivotal role in driving opinion seeking,impulsive and compulsive buying behaviors among consumers. Empirical findings reveal a lackof consumer awareness regarding the environmental and ethical consequences of ultra-fastecommerce purchases, and skepticism toward sustainability claims made by low-pricecompanies. However, consumers demonstrate high trust in influencers, who play a significantrole in shaping purchasing decisions, particularly regarding ultra-fast ecommerce. By shedding light on how ultra-fast ecommerce marketing strategies affect consumer behavior,this research contributes to academic scholarship and offers a range of practical implications.We offer a deeper insight into how consumers make choices and suggest ways to encouragepro-sustainable shopping habits in the ecommerce marketplace. Ultimately, this studyunderscores the urgent need for more studies focusing on regulatory frameworks, industrystandards, consumer education initiatives together with tailored marketing strategies that alignwith consumer values and how to promote ethical consumption practices to reduce the negativeimpact of ultra-fast ecommerce on the environment and on ethical aspects. By empoweringconsumers with knowledge and promoting ethical alternatives, we can encourage moreconscious and responsible purchasing decisions, ultimately contributing to a more sustainableand equitable digital marketplace.