Abstract MJ15, a novel cannabinoid CB 1 receptor selective antagonist was discovered. In receptor binding assays, MJ15 displayed a high affinity for rat cannabinoid CB 1 receptor ( K i = 27.2 pM, and IC 50 = 118.9 pM), but a much lower affinity for rat cannabinoid CB 2 receptor (only 46% inhibition at 10 μM). At the cellular level, the IC 50 values against activation of cannabinoid CB 1 and CB 2 receptors induced by Win55212-2 in specially designed EGFP—CB 1_U2OS and EGFP—CB 2_U2OS cells were 0.11 μM and > 10 μM, respectively. In addition, MJ15 dose-dependently blocked Win55212-2 mediated increase of intracellular Ca 2+ levels in hippocampal cells and reversed the inhibitory effects of cannabinoid CB 1 receptor agonist on forskolin-stimulated adenylyl cyclase activity in CHO cells expressing the human cannabinoid CB 1 receptor. In animal experiments, MJ15 demonstrated remarkable effects from 20 to 40 mg/kg, including promoted the small intestine peristalsis in ICR mice and inhibited food intake and body weight increase in diet-induced obesity (DIO) rat and mouse. 40 mg/kg MJ15 significantly reduced food intake at initial 2 weeks of treatment, prevented the increase of body weight and adipose by 46% and 28% respectively in DIO rats, and reduced body weight and adipose gain by 70% and 23% respectively in early onset obesity DIO mice after 4 weeks treatment. Meanwhile, dyslipidemia were ameliorated in both models. Taken together the in vitro and in vivo data, MJ15 is demonstrated to be a potent and selective cannabinoid CB 1 receptor antagonist and holds a prominent potency in obesity and dyslipidemia treatment.