Seven hundred and fifty nonreplicated clinical isolates of Pseudomonas aeruginosa were collected from five hospitals during March 2007 to May 2009. Forty-one isolates (5.46%) were characterized as multidrug-resistant P. aeruginosa (MDRPA). PCR assays were used to detect class 1 integrons. Amplifications of internal variable regions (IVRs) of class 1 integrons revealed three different arrays (0.8, 1.3, and 1.7 kb) with different distributions in clinical isolates. The amplified IVRs were sequenced and three gene cassette arrays including aadB (0.8 kb), aadA6-orfD (1.3 kb), and bla(OXA10)-aacA4 (1.7 kb) were identified. In conclusion, we confirmed the high prevalence of class 1 integons with limited diversity of gene cassette arrays in MDRPA clinical isolates found from five hospitals. This is the first report showing gene cassette contents of class 1 integrons in P. aeruginosa isolates in Iran.