•Immune checkpoint inhibitors emerged as a the predominant 2L treatment, leading to a substantial decrease in the utilization of chemotherapies beyond the 1L.•Despite the introduction of immune checkpoint inhibitors, treatment attrition rates remained elevated, with approximately only half of patients undergoing ICIs the post-ICIs era.•When comparing the outcomes of patients treated before and after the introduction of ICIs, we did not observe higher rates of either a 2-year OS or an increase in the number of patients receiving 3L therapies. Metastatic urothelial carcinoma (mUC) is a lethal disease with limited treatment options. We aimed to compare the treatment patterns and outcomes of patients with mUC who were treated before and after the introduction of immune checkpoint inhibitors (ICIs) at a tertiary hospital in Barcelona. Single-center retrospective study from 2004 to 2021. Access to ICIs began in December 2014. We analyzed differences in clinical characteristics and survival outcomes, such as overall survival (OS), progression-free survival (PFS), and restricted mean survival time (RMST). A total of 206 patients were included. The median follow-up was 48.6 months. Ninety and 116 patients were treated during the pre-ICIs and the post-ICIs eras, respectively. We found high treatment attrition rates, with no differences in the number of patients who received second-line (48%) and third-line (26%) therapies between the two eras. In the second-line, ICIs became the predominant therapy (58%), leading to a 30% reduction in the utilisation of platinum-based ChT and non-platinum ChT. Innovative approaches including ICIs in the first-line treatment (18%) and targeted therapies in the third-line setting (34%) were observed. We found no differences in the median OS, 2-year OS, or 24-month RMST between the two periods. ICIs have emerged as a transformative treatment option, reshaping the treatment landscape. Nevertheless, substantial attrition rates from first-line to subsequent lines of systemic therapies might impede the potential impact of ICIs on long-term survival outcomes across the entire population. Immune checkpoint inhibitors now serve as a novel treatment option for patients facing metastatic urothelial carcinoma, particularly in the second-line setting, thereby changing the treatment paradigm. Nonetheless, the substantial attrition rates during the transition from the first-line to subsequent lines of systemic therapy may hinder the potential impact of immune checkpoint inhibitors on long-term survival outcomes for the broader population.