Introduction: The present systematic review and network meta-analysis (NMA) of randomized controlled trials (RCTs) aimed to compare the mortality rates related to adverse events (AEs) and discontinuation of treatment due to toxicity as well as all AEs of currently used chemotherapy regimens for first-line therapy of advanced or metastatic urothelial carcinoma of the bladder (UCB). Material and methods: The MEDLINE and EMBASE databases were searched for articles published between January 2000 and June 2020 according to the Preferred Reporting Items for Systematic Review and Meta-analysis extension statement for NMA. Eligible studies included RCTs comparing different first-line chemotherapy regimens for treating advanced or metastatic UCB and AEs as outcome measures. A NMA was performed to assess the mortality rates related to AEs and discontinuation of treatment due to toxicity as well as all AEs. Results: Fourteen trials comprising 2,615 patients met our eligibility criteria and formal NMAs were conducted. Results revealed that gemcitabine plus carboplatin had the lowest likelihood of mortality related to AEs (P score: 0.8079), while larotaxel plus cisplatin and paclitaxel, cisplatin plus gemcitabine had both a lower toxicity rate leading to discontinuation (P score: 0.7295 and P score: 0.7242, respectively). Compared with gemcitabine plus cisplatin (GC), most chemotherapy regimens were associated with a lower likelihood of thrombocytopenia, anemia, and cardiovascular toxicity. In contrast, most chemotherapy regimens compared with GC were associated with a higher likelihood of neutropenia, central (fatigue, neuropathy) and gastrointestinal AEs, infections, as well as renal and pulmonary toxicities. Conclusion: Results of the present study demonstrated that hematological toxicity was the most prevalent AE associated with gemcitabine-containing regimens, while central AEs and febrile neutropenia were more commonly in taxane-containing regimens. GC had the lowest rate of gastrointestinal AEs, infection disorders, and pulmonary toxicities. Cisplatin-containing regimens were associated with a higher rate of renal and cardiovascular toxicity. These differential AEs may help in the detection of the personalized therapy in addition of efficacy data.