Background: Carbonated soft drinks (CSD), packaged in PET (polyethylene terephthalate) bottles, are among the most widely consumed non-alcoholic beverage globally. People of all ages enjoy CSDs for their flavour, mouthfeel, crispness, freshness, and capacity to both quench thirst and provide mental refreshment. Terephthalic acid, ethylene glycol, and other additives such as phthalates are the materials used to make these PET bottles. Several studies have demonstrated that phthalates may migrate into packaged goods and, when consumed, can cause several ill-health conditions to humans. Type II diabetes, obesity, asthma, male and female reproductive disorders, tumours (including breast cancer), pituitary, hypothalamic, and peripheral hormone disorders, behavioral issues, and neurodevelopmental disorders are among the health issues reported to be associated with phthalates. Objective: This study aimed to ascertain the presence and concentration of phthalates in PET bottled carbonated soft drinks produced in Mwanza City, and to examine the effects of various storage conditions on the migration of these contaminants into the product. Methods: Liquid-liquid extraction, clean-up techniques, and chromatographic analysis were used as the methods of determination to identify and quantify the specific phthalates compounds. Results: The findings demonstrated that after being stored outdoors for four to six months, the migration, especially for dibutyl phthalate (DBP) and di [2-ethylhexyl] phthalate (DEHP), became more apparent. After two, four, and six months of indoor storage, there was no appreciable change in the mean concentrations of DMP (dimethyl phthalate), DEP (diethyl phthalate), DBP (dibutyl phthalate), and DEHP for either brand in this study. Compared to indoor storage, the DBP and DEHP migration increased by up to 24-fold when the two brands were kept outdoors for four and six months. Thus, the safety and quality of carbonated soft drinks were seriously compromised by the phthalate compounds from the PET bottles that these companies were using. Conclusion: The study's conclusions show that PET packaging, which is influenced by the bottle manufacturing process and raw material formulations for packages of the studied CSDs, are responsible for the migration of phthalates into the products. The storage conditions and time are established to be the primary causes of phthalates migration in bottled carbonated soft drinks. Though the migration figures in this study are lower than those of the other studies from different locations that were compared, it is important to remember that these compounds may interfere with hormones even in small quantities.