We characterized the molecular basis of carbapenemase production in carbapenem-resistant Gram-negative bacteria isolated from hospitalized patients from Saudi Arabia in the year 2012. Isolates were collected from across the Kingdom and phenotypically tested for carbapenemase production. Polymerase chain reaction detection of carbapenemase genes was also performed. Our results indicate that in Saudi Arabia, OXA-48 and NDM-1 are the dominant carbapenemases among Enterobacteriaceae with low prevalence of VIM. The latter is the most prevalent metallo-beta-lactamase in Pseudomonas aeruginosa, whereas oxacillinases, OXA-23 in particular, are the dominant carbapenemases in Acinetobacter baumannii. No KPC or IMP genes were detected. Our study is the first report of OXA-48, NDM-1, and VIM-4 enzymes in Enterobacter from the Kingdom. Also it is the first report of OXA-72 and NDM-1 in A. baumannii in Saudi Arabia, and the coexistence of blaOXA-23 and blaNDM-1 genes in this species in the country. Awareness of the role of international travel in the spread of carbapenem-resistant determinants in the Kingdom, as well as effective infection control interventions in hospitals and strict antimicrobial stewardship in healthcare facilities and the community are keys to combat the rise of carbapenemase producers in the Kingdom.