Abstract Body: A growing body of work supports that the adipokine chemerin contributes to vascular contractility, normal blood pressure, and adiposity-associated hypertension—by mechanisms thought to be sexually dimorphic. Mechanistic chemerin research in whole animals has hinged on two key tools: an antisense oligonucleotide (ASO) against chemerin, and recently, a global genetic chemerin knockout (KO) in the Dahl SS rat. Previous work with the whole-body ASO against chemerin showed that chemerin drives adiposity-associated hypertension in males and females equally. Recent developments in ASO design prompted us to test whether the ASO against chemerin reduced blood pressure by preventing chemerin production only. Yet, upon administering the whole-body ASO to the KO rat, blood pressure was lowered in both wild-type (WT) and KO rats, indicating that the ASO had off-target effects on blood pressure, likely due to backbone-dependent effects of the ASO. This necessitated use of the KO rat to better understand chemerin’s true role in vascular health and disease. Using Dahl SS chemerin WT/KO rats fed control (CD, 10% fat) or high fat (HFD, 60% fat) diets from weaning, we tested the hypothesis that genetic loss of chemerin would reveal chemerin’s role in driving adiposity-associated hypertension, vessel stiffness, and changes in sex hormone levels. Telemetric reports of blood pressure showed that the KO blunted development of HFD-induced hypertension in males but, intriguingly, exacerbated it in females. Pulse wave velocity analysis indicated that aortic arch stiffness was lower in the KO male rat on HFD vs the WT male on HFD, but no differences were observed between WT and KO in either the C or HFD females. Interestingly, ELISA of plasma showed progesterone was reduced in female HFD KO vs female HFD WT. Dihydrotestosterone levels were increased in male HFD KO and female CD KO compared to their WT counterparts. Our results with the chemerin KO (summarized in Table 1) highlight a sex-dependent role of chemerin in cardiovascular disease that was previously missed with the ASO. We provide support that chemerin drives adiposity-associated hypertension and vascular stiffness in males but protects against these pathologies in females. We also show that loss of chemerin influences sex hormone levels in a sexually dimorphic manner. Discovery of chemerin’s sex-dependent role prompts further research into chemerin as a therapeutic target in both cardiovascular and sex-specific diseases.