Chlamydia (CT), gonorrhoea (NG) and syphilis (TP) infections are rising and have an important burden in the EU/EEA. This study aims to describe the epidemiology of these infections in Portugal, between 2015 and 2018, in order to set a baseline for the recently created National Strategy for STI Control and to generate hypothesis on areas for improvement. We analysed data from the national system of epidemiological surveillance (SINAVE®) and described all probable and confirmed cases of CT, NG and TP notified in Portugal between January 1st, 2015 and December 31st, 2018.This reports the overall case evolution as well as specific characteristics of different groups. Throughout the analysed 4-year period there were 1267 cases of CT, 1917 of NG and 3240 of TP (probable and confirmed). Of CT cases, 70% (n = 891) occurred in males, 66.3% (n = 840) in people aged 18-35, 52.9% (n = 670) in heterosexuals and 42.9% (n = 543) in men who have sex with men (MSM). Of NG cases, 87.9% (n = 1686) were males, 90.8% (n = 1741) were <45 years-old and 51.2% (n = 982) were MSM. Of TP cases, 76.0% (n = 2462) were males, 64.8% (n = 2101) were <45 years-old, 41.1% (n = 1333) were heterosexuals and MSM accounted for 39.9% (n = 1294). The notified cases have doubled from 2015 to 2018 (1159 to 2354) and tripled in MSM (440 to 1312), with a 7.9, 4.1 and 1.6-fold increase in CT, NG and TP, respectively. For each infection, symptomatic cases contributed to 42.9% (CT), 14.6% (NG) and 81.9% (TP) of the overall. In similarity to European trends, CT, NG and TP infections seem to be rising in Portugal. Changes in patient behaviour, clinical practice, screenings, settings of diagnosis and notification should be further explored to better understand this trend, including clinical features. From our results, MSM and people aged <45 should be prioritised within the National Strategy for STI Control. A surveillance system evaluation could be considered for sensitivity and usefulness. Key messages The number of chlamydia, gonorrhoea and syphilis reported cases in Portugal raised in the four-year period between 2015 and 2018, with MSM accounting for 54.6% (1312/2403) of the cases in 2018. This sets up a baseline to guide the adoption of specific measures and the prioritisation of interventions. MSM should be given special attention when addressing new prevention strategies.