Anacyclus valentinus L. is a common annual plant in Algeria, known for her various therapeutic effects. In addition, the plant is used as a food condiment. We reported our investigations on the chemical compositions and the antiarthritic activity of methanolic extract of A. valentinus (MEAV). The polyphenol extraction by maceration with methanol (80%) gave yields of 17.82%. The identification by LC-MS and colorimetric assays revealed the wealth of methanolic extracts on phenolic compounds including flavonoids (52.15 mg Equ/g) and lactones. Acute oral toxicity of extract was performed in line with OECD guidelines and the lethal dose 50 was assessed greater than 2500 mg/Kg. Regarding the anti-arthritic power, rheumatoid arthritis was induced by Freund's adjuvant in rats. The methanolic extract of A. valentinus presented a largest effect with weight gain, an arthritic score, thymus indices; spleen and serum parameters close to those of the control. The extract also inhibited edema and restored cartilage structure.