Neisseria gonorrhoeae antimicrobial resistance (AMR) and gonorrhea disease burden remain major public health concerns worldwide. To contribute to the supranational demands to monitor and manage the spread of antimicrobial-resistant N. gonorrhoeae, the Portuguese NIH promoted the creation of the National Laboratory Network for Neisseria gonorrhoeae Collection (PTGonoNet). The present study reports the N. gonorrhoeae major AMR trends observed from 2003 up to 2018. All isolates described in the present study constitute the opportunistic ongoing N. gonorrhoeae isolate collection supported by the National Reference Laboratory for Sexually Transmitted Infections of the Portuguese NIH, enrolling strains isolated in 35 different public and private laboratories. Minimum inhibitory concentrations were determined using E-tests for azithromycin, benzylpenicillin, cefixime, ceftriaxone, ciprofloxacin, gentamicin, spectinomycin and tetracycline. Molecular typing was determined using NG-MAST. AMR data of 2596 country-spread isolates show that 87.67% of all N. gonorrhoeae isolates presented decreased susceptibility to at least one antimicrobial. A continuous decreased susceptibility and resistance to penicillin, tetracycline and ciprofloxacin can be observed along the years. However, no decreased susceptibility to cephalosporins was observed until 2018, while for azithromycin, this was always low. The most common observed NG-MAST genogroups were G1407, G7445, G225, G2, and G1034. This study evidences the advantages of a nationwide collection of isolates and of centralized AMR testing to respond to supranational (EURO-GASP) requirements while providing unprecedented data on AMR in the context of 15 years of surveillance.