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Antibiotic resistance is a growing global threat, driven by the widespread use of antibiotics in healthcare and agriculture. Wastewater treatment plants and the environment serve as reservoirs for antibiotic-resistant bacteria (ARBs) and antibiotic resistance genes (ARGs). This study investigated how mobile genetic elements (MGEs) contribute to the spread of ARGs in Swedish aquatic environments. Water and sediment samples were collected from both incoming and outgoing wastewater, as well as from the surrounding environments. Enterobacterales, Shewanella, and Vibrio bacteria were isolated, and antibiotics were tested using the disc diffusion method. The highest resistance to antibiotics was observed in incoming wastewater against tetracycline and streptomycin, indicating widespread use of these antibiotics. Resistance to antibiotics, including meropenem, ciprofloxacin, and sulfamethoxazole-trimethoprim, increased in outgoing wastewater, indicating that wastewater treatment plants do not eliminate all resistance. Environmental sediments showed more diverse resistance than surface waters, likely due to their ability to bind and protect antibiotics, creating favorable conditions for the maintenance of ARGs. Conjugation assays showed that resistance traits could be transferred to a susceptible E. coli strain, confirming the mobility of resistance genes. Antibiotics and resistance genes are present in groundwater, which may impact both the environment and public health. More research and better monitoring are needed to reduce these risks in the future.