The objectives of this study were to describe and compare the clinical characteristics of ankylosing spondylitis (AS) and undifferentiated spondyloarthritis (USpA) in Middle East Arab (MEA) and South Asian (SA) patients diagnosed in our unit. Fifty-eight consecutive patients diagnosed with SpA were studied after classifying them into MEA and SA. They were further classified as per disease diagnosis. Excluding three patients with miscellaneous ethnicity, there were 29 MEA and 26 SA patients. Seventy-two percent of MEA patients were males (vs 92% of SA patients). Of the 29 patients with MEA ethnicity, 17 had AS and 9 had USpA. Of the 26 patients with SA ethnicity, 10 had AS and 14 had USpA. Fifty-nine percent of MEA patients had AS (vs 39% of SA patients). Mean age at onset in AS patients was similar in the two ethnic groups. However, in patients with USpA, mean age at onset was somewhat lower at 21.8 years in the MEA group compared with 29.4 years in the SA group. Family history in first-degree relatives was significantly more common in MEA patients. Weight loss, inflammatory spinal pain, gluteal pain, and enthesopathy were equally common in both ethnic groups. Knee, ankle, and metatarsophalangeal joint involvement was less common in MEA patients. There were no significant differences in the occurrence of syndesmophytes, bamboo spine, and sacroiliitis in the two ethnic groups. HLA-B27 positivity rates in MEA patients were 87% for AS and 67% for USpA compared to 75 and 71%, respectively, in SA patients. It is concluded that some significant new findings have arisen from this study: the majority of MEA patients presented with AS, whereas the majority of SA patients had a picture of USpA. Family history was more common in MEA patients. Peripheral arthritis was less common in MEA patients. Worldwide, this is the first study to show that there are significant differences in the clinical expression of the various SpA in MEA patients compared to SA patients.