The objective of this study was to assess the prevalence of the Mediterranean FeVer (MEFV) gene mutations in systemic lupus erythematosus (SLE) patients and their effect on organ involvement, as well as disease activity and severity. The frequencies of three familial Mediterranean fever-related MEFV gene mutations (M694V, V726A and E148Q) were investigated in 70 SLE patients. Organ involvement, Systemic Lupus International Collaborating Clinics/American College of Rheumatology (SLICC/ACR) damage index and Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) scores were correlated with mutation carriage. Eleven of 70 patients (15.7%) were found to carry an MEFV mutation. A single patient harbored two mutations, E148Q and V726A, without overt familial Mediterranean fever while the rest were heterozygous carriers. Four of the 11 carried an M694V mutation, four carried V726A and two carried E148Q. The majority of MEFV mutation carriers were Sephardic while non-carriers were mainly of Ashkenazi origin (72.7% vs. 45.7% and 47.4% vs. 9.1%, respectively, p = 0.02). SLE onset was significantly earlier in MEFV carriers (27.6 ± 9.7 vs. 38.2 ± 15.5 years, in carriers vs. non-carriers, p = 0.02). Hematologic and serologic parameters were comparable among mutation carriers and non-carriers. Febrile episodes were more common among MEFV mutation carriers (45.4% vs. 15.2%, p = 0.035) and there was a trend for excess episodes of pleuritis as well (54.5% vs. 23.7%, p = 0.06 in carriers vs. non-carriers, respectively). The frequency of secondary anti-phospholipid antibody syndrome was equivalent among the groups. Conversely, compound urinary abnormalities and renal failure was not observed among MEFV carriers yet was present in 33.4% and 18.6% of non-carriers (p = 0.027 and 0.19, respectively). SLICC damage index and SLEDAI activity index did not differ significantly between the groups. MEFV mutation carriage appears to modify the SLE disease phenotype in that it contributes to an excess of inflammatory manifestations such as fever and pleuritis on the one hand, while thwarting more severe renal involvement on the other.